I made my blog solar-powered, then things escalated | Hacker News Reader

I made my blog solar-powered, then things escalated

louwrentius.com

307 pointsjandeboevrie219 comments

Tip to OP (I think they already have this idea, based on the post): when that lead-acid battery dies, replace it with a LiFePo4, which is substantially more efficient, lasts 3x as long, has a higher energy density, provides a usable voltage far further into its discharging %, etc. etc... A couple pages that describe the differences linked below...

tl;dr if you are starting a solar battery project, LiFePo4 is the clear choice by far, unless you're going for the absolute cheapest possible build due to immediate budget constraints.

https://www.canbat.com/a-detailed-comparison-of-lead-acid-ba...

https://www.power-sonic.com/blog/lithium-vs-lead-acid-batter...

I don't disagree with you but lifepo4 have a high upfront one time purchase cost for something equivalent in capacity to a 12V 100Ah AGM, like easily $450-500 per unit or more. They do pay for themselves over time with their much greater longevity.

Might be more than the blog owner wants to spend for what is just a fun hobby project.

There are some 3U rackmount size nominal 48vdc 50Ah lifepo4 (approx 4.8kWh capacity) with built in bms and LVD you can get from china now.

Yeah, there's def the upfront cost, which not everyone can justify. Though, at the same time, a lower-amp-hour battery can provide as much actually-usable energy as a higher-amp-hour-rated SLA battery (so you could purchase a LiFePo4 battery with a lower amp-hour rating than the equivalent SLA battery but still get the same run time). I wouldn't know how much lower you can go though offhand.

With lead acids you just have to make sure you don't go below 40% charge. They don't tend to like that. The deep cycle ones are a bit better but I've experienced them deteriorating quickly too once you go too low. The other disadvantage is that they are quite heavy and might end up taking up lots of space. I'm personally still using lead acid, but with plans to go LiFePo4.

If you can't go below 40%, it might make sense to reduce the capacity by 40% accordingly when making comparison calculations against tech that can do that no problem. How does bang for buck look then with SLA versus LiFePO4?

I don't have the exact numbers but even then it's cheaper. The only issue is - can you trust yourself (or your planning) to ensure you don't go below 40%? Real life is hard to plan.

What happens if you do let it go below 40% (either as a brief dip to high 30s, or letting it go to 0)? Is it closer to a case of "oops you hit 39%, this battery is now worthless" or "oops you went down to 0%, better not do that every day as statistically the battery will last 0.001% less long"?

edit: I pasted my comment (prefaced with "context = lead-acid batteries") into ChatGPT and got this answer, maybe someone who knows could, instead of having to explain it all to me, just confirm GPT-4 got it right, or if not the correct it / add detail?

> If a lead-acid battery is allowed to go below 40% state of charge (SOC), it can cause some issues, but the effects are not necessarily immediate or catastrophic. The depth of discharge (DoD) and frequency of these deep discharges can impact the battery's overall lifespan and performance.

> 1. Brief dip to high 30s: If the battery's SOC occasionally dips into the high 30s, it may not cause significant harm. However, consistently discharging to that level can gradually decrease the battery's overall lifespan.

> 2. Discharge to 0%: If a lead-acid battery is allowed to discharge to 0%, it can cause more serious damage. Repeatedly discharging the battery to this level will dramatically shorten its lifespan and could potentially cause it to fail prematurely.

> The relationship between DoD and battery life is not linear. For example, discharging a battery to 50% DoD might give you around 1,000 to 1,200 cycles, while discharging it to 80% DoD might give you only 300 to 500 cycles. It is generally recommended to keep lead-acid batteries at a higher state of charge to maximize their lifespan and maintain optimal performance.

> In summary, allowing a lead-acid battery to occasionally dip below 40% SOC may not cause immediate damage, but consistently doing so can reduce its lifespan. Discharging the battery to 0% can cause even more significant harm, especially if done repeatedly. It is best to keep lead-acid batteries at a higher state of charge to ensure their longevity and maintain optimal performance.

ChatGPT is not wrong... but in my personal experience, once you go below 40% it's all downhill from there. At least if you've done it 2-3 times. Batteries are not always exactly the same, and temperature conditions vary as well. I've been nursing batteries for years, and this is just my anecdotal comments on that.

One thing that we can all agree on though is that you must never ever use car batteries. Lead acid need to be the deep cycle kind.

More deets from ChatGPT

> please provide an example data to show non-linar relationship between DoD and lifespan in 5% increments.

Depth of Discharge (DoD) Approximate Number of Cycles 05% 3,500 - 4,000 10% 3,000 - 3,500 15% 2,500 - 3,000 20% 2,000 - 2,500 25% 1,800 - 2,200 30% 1,600 - 2,000 35% 1,400 - 1,800 40% 1,200 - 1,600 45% 1,100 - 1,400 50% 1,000 - 1,200 55% 900 - 1,100 60% 800 - 1,000 65% 700 - 900 70% 600 - 800 75% 500 - 700 80% 300 - 500 85% 200 - 400 90% 100 - 300

> thinking through the following steps please create an asci bar chart for this table, dod given in 5% increments:

1. Calculate the number of cycles for the first increment 2. Extract the maximum number 3. Calculate the number of stars with 1 start = 500 cycles 4. Put number of starts into a table 5. iterate over the table

Once the table has been completed create the asci bar chart plotting DoD vs Cycles

Example: 1. 5% DoD = 3,500 - 4,000 2. 4000 3. 8 stars

DoD Cycles

05% ********

10% *******

15% ******

20% *****

25% ****

30% ****

35% ***

40% ***

45% **

50% **

55% **

60% **

65% *

70% *

75% *

80% *

85% *

90% *

Lol, the way this came out to sit perfectly with OP's intuition. Even down to the drop from 2-stars to 1-star!

48v 100ah LifePO4 is under 1000$ in China

It is but you have to make very sure that you actually get what you ordered and not some substitute with lower grade cells than what's advertised.

Are there easy(/cheap) ways to verify this if one does buy, as an individual, a cheap battery like that? Or do you need to either rely on brand reputation or have access to expensive equipment for testing?

I think vendor reputation is almost as important (or maybe even more important) as brand reputation. In many cases a brand is just a sticker, and your vendor may well have a longer relationship with their customer.

For instance, telling a brand name cell from a fake cell can be extremely hard, but your vendor knows exactly where they bought them. I buy cells from nkon.nl, who are a high rep local vendor and I've yet to be disappointed but buying a pack that is sealed from a low rep vendor may well incur a lot of risk. You'd almost have to split open the shrink wrap to make sure you got what you paid for. One quick and dirty way to check is to weigh the pack and to compare the weight to the manufacturers spec for the cells. It's obviously not perfect but many fake cells have weights that are wildly different from the cells they pretend to copy (usually due to much lower actual capacity).

You can do a capacity test quite easily, that will only tell if the capacity is the rated one. You will have to check for physical signs of bad cells, they enlarge (bloat), but that means you need to open the case (sometimes it will void any warranty) and check each cell.

Discharge & record the curve. All it takes is one poor-performing cell & your whole pack is going to be hurting bad. Discharge down to like 2.85V * number of cells. The curve should be nice & even. If there are places where the voltage drops before the big drop at the end, it's a sign that one cell isn't performing.

If your has equalization, try to discharge & equalize charge it 2-3 times first.

If you can actually get access to the cells, measuring cell resistance is not expensive. Anomolies will show themselves very quickly. Everything should be pretty clumped together in internal-cell-resistance. If you have a pack equalizer, it can be used to help you read this out. My <$100 charger has a cell resistance test mode.

> All it takes is one poor-performing cell & your whole pack is going to be hurting bad.

Yes, that can't be stressed enough. And depending on the fault and how the BMS handles it a more dangerous condition could easily develop. For instance an undetected short would cause the other batteries to be overcharged to the point where they are much more likely to die themselves, and some of those may do so in pretty violent ways.

Cheap / missing BMS are a serious problem with cheap Lithium-Ion packs, they are the first line of defense and bad cells can even happen when supplied by good brands (but the chances are a lot higher with no-name stuff).

Another good test: charge the pack, balance it, measure the pack voltage and the individual cell voltages, then let it rest for a day or two and measure again. Any kind of deviation between cells is a sure sign something is not working well and is the earliest warning sign for trouble you can get. The rate of self discharge should be the same for all cells and it should be very low, too low to measure (and make sure you disable the balancer after the initial charge!). After a month or so it would be fine to see the pack drop a little bit, but not a lot.

Yet another quick test: use an IR camera to look at the pack both during charging and at rest. Any cells that are warmer than those around them are suspect.

Are these more or less a plug in replacement for lead acid, likely to work with our existing charge controller?

Not all are, but the Simpliphi batteries are designed to be plug-in replacements more or less

Most charge controllers made for serious applications allow for the selection of battery chemistry.

It seems not: https://www.power-sonic.com/blog/how-to-charge-lithium-iron-...

They may work for the the initial phases of charging but not for “float” I.e keeping the battery as close to 100% charge over a longer period.

By far… not so. Just, marginally, as of the last year, perhaps - but the total cost over the lifetime per Wh of storage is still on a par with lead, because lead acid batteries are cheap as chips, require little or no maintenance if you’re sealed, and if you get something like OPzS cells and treat them well, you will get 20 years of life from them. LiFePo4, you’re looking at a decade, maximum, before they’re trash.

I set us up here, totally off grid, three years ago, using a bank of OPzS cells, giving us 42kWh of usable storage. I rarely take them below 70%. Their performance has barely budged since installation, and with the condenser caps, they have required zero maintenance - I check the specific gravity of the acid once a year, and go “yup”, and that’s it.

LiFePo4 I am considering for a booster bank at our cabin, which is 500m from our power shed, as the cable limits us to ~2.5kW here before we see significant voltage drop - it’s either that or step-up/step-down at either end, but transformers are surprisingly expensive. Main reason I’m leaning towards them for this application is mass, as our only access is either by foot or an aerial cableway - our lead bank weighs about 2000kg, equivalent LiFePo4 is about 450kg.

So - LiFePo4 is a decent choice, but depending on your application, a pile of big lead acid cells can be better. See, for instance, storage at various solar projects - it’s virtually all OPzS cells, as the amortised cost is still favourable.

> LiFePo4, you’re looking at a decade, maximum, before they’re trash.

I think they will be at 80% after a decade, thus not trash.

> if you’re sealed, and if you get something like OPzS cells and treat them well, you will get 20 years of life from them.

If you have the space, 6V or even 2V OPzS cells can be huge.

Mine are 2v 660Ah cells - 24 of them take up about 3m^2 of floor, and they’re about 80kg each. Power density, they do not have.

Thank for sharing, almost 2 ton in weight. But I believe that can work.

Idk. For a ten year battery in a nightly discharge application you get 0.28 AH for each amp he purchased even with the OPzS cells. First you have to diéntate to .7 for a nightly discharge rate, then to reach 10 years of life span you have to de rate to 0.4 depth of discharge .

So if for example, you need 1600 AH, you would spend $1500 for a 2000 AH lLiFe02 bank, plus 150 for a decent BMS, so $1800 US including shipping. (Just bought our 5th and 6th banks)

For the OPzS, you would need to buy 5714 AH to get the same cycle life and longevity, plus you have to write off 38 percent of your charging energy due to voltage and discharge rate discrepancies vs about 10 percent for the LiFeO2.

I seriously doubt you could obtain 5700 AH, shipped to your location, for less than $1800.. and then the size, maintenance, and corrosion issues (some of that goes away with the considerably more expensive sealed designs) also add to the headache.

If the battery magazine will be subject to below freezing temperatures, both types incur additional risks and energy costs for the lithium, you must heat it prior to charging. For the lead, you will need to add another 40 to 50 percent capacity to meet your target power capacity.

TIL. For non native speakers: "specific gravity" means "density, typically relative to max density liquid water", which does not make sense to me at all.

It's a simple way to check changes in concentration of a chemical in water when you're not worried about external contaminants (i.e. just water vapor or anticipated chemical reactions).

For home brewers, measuring specific gravity at the start and end of your brew process is the simplest way to know how much alcohol is in your creation. For this you'd use a hydrometer: https://en.wikipedia.org/wiki/Hydrometer

It is a common way to measure battery charge through a hydrometer in automobiles batteries (not the sealed type):

https://en.wikipedia.org/wiki/Hydrometer

>Battery hydrometer

The state of charge of a lead-acid battery can be estimated from the density of the sulfuric acid solution used as electrolyte. A hydrometer calibrated to read specific gravity relative to water at 60 °F (16 °C) is a standard tool for servicing automobile batteries.

Isn't charging efficiency for lead acid lower tho ? Then again if you save on batteries might as well get that extra panel or two

Yes, LiFePO charges much faster and in solar setups can "use more of the input" when it does shine. Lead-acid can compete there mostly by building a much bigger battery pack.

I'd personally not want a lead-acid battery burping flammable gas inside an apartment. They're supposed to be installed in ventilated spaces with drainage holes for any acid that spills out.

Or you have recombiner caps - haven’t had to top up at all, as they turn the escaping O/H back into water.

Unless you will be in cold temperatures, then LiFePo batteries will die if you charge them.

How cold is "cold" ? Here in the Netherlands we rarely get more than a couple of days per year with temperatures much below zero.

Below freezing seems to be the standard rule[1]. One typical solution is to use the charging current to heat up the battery instead until it's above freezing, then start the charging.

You could of course also use some of the charge from the battery itself to heat it up.

[1]: https://relionbattery.com/blog/lithium-battery-cold-weather

Anything below 0C is problematic for LiFePo4.

I have a small solar powered device (Pi Zero controlling an antenna switch) in my backyard that I use a little mechanical temperature switch to turn on and off a teeny tiny mat heater attached to the battery. It's all in an enclosure that's water tight, so I doubt it got below 0 during the day in there in the first place. We didn't get temperatures below 0C this winter in the NE USA (which is not ordinary), and even with some dips below 0 the battery seems fine.

I've addressed LiFePo4 in my blog and why I'm not yet running this.

I'm trying to respond to some comments, but since this is not my thread, I'm rate-limited.

> Let's talk about the battery. I've chosen to use a large used lead-acid battery even though Lithium (LiFePO4) batteries beat lead-acid in every metric. I bought the battery second-hand for €100 so that's not a significant investment for a battery. Although it's a bit worn-down and the capacity is reduced, it is still good enough for me to run my computer setup for 10 hours after a full charge. The lead-acid battery also serves another purpose: is a relatively cheap option for me to validate my setup. If it works as intended, I might opt to upgrade to lithium (LiFePO4) at some point."

I think the rate limiting is not based on which thread you're active in, but whether the mods have placed a rate limit on you. It's hard to say since it's not very transparent, but it seems the mods here are pretty liberal about dispensing permanent rate limit penalties.

Thanks, the limit seems removed now. With my own submissions I’m never rate limited.

How safe are LiFePo4 batteries these days? Can one use these in -20 to +60 degrees Celcius environments without a fire hazard?

I'm asking because I'm creating a similar setup to OP to control the climate in my glider's trailer.

LiFePo4 are the safest of the commercially available lithium batteries. They can still catch fire if you insist, but it is nothing like the kind of batteries typically found in cell phones that can readily turn into fireworks. Some models are rated from -20C to 60C.

Lead acid also have their own set of problems. Some types can produce hydrogen gas while charging, which can be an explosion hazard in an poorly ventilated room. Also, all types of battery are energy storage, and in case of a short circuit, they will release a lot of it as heat, and even if the battery itself can handle it, it can ignite flammable material in the vicinity.

Any lithium battery claiming to be rated for operation down to -20 C is likely lying. Lithium chemistries are sensitive to temperature and operate well in a narrow temperature range. Operation below freezing ambient temperatures requires a heater and heaters need energy - hence why they are uncommon and only add cost.

Au contraire, lead-acid batteries work pretty well at temperature extremes, needing only changes in charging (e:) voltage and being limited by discharge current.

GP said rated, not necessarily for operation. It could just mean that the battery will survive such low temperatures unharmed.

I have a summer cabin with a solar panel and a couple 12 V lead acid batteries. It would be great to be able to install some lithium type batteries instead, so long as I know they will survive winter.

Any lithium battery claiming to be rated for operation down to -20 C is likely lying.

Not necessarily lying but rather there are heating pads that use some of the energy to bring the battery up to safe operating temperature based on BMS readings. There are some LiFePo4 battery breakdowns on Will's YouTube channel that show the various heating pads used by each vendor. [1] So probably better to say they leave out some details that will affect capacity at lower temperatures. He has a HN account so maybe he will also comment.

[1] - https://www.youtube.com/c/WillProwse/videos

That’s exactly my point though - if you are aiming for robust operation at a wide temperature range, lithium batteries are actually a worse choice than lead acid batteries. Lead acid batteries require little to no temperature control, just some charging rate and voltage control depending on temperature.

I wasn't actually disagreeing with you, just pointing out that at worst the companies are lying by omission. That said I don't think there is a one size fits all. LiFePo4 are great where weight matters more than temperature such as boats, RV's or anything that is mobile. The power used by the heating pads in some cases is offset by the higher capacity and ability to maintain voltage at lower charge state.

For off-grid buildings lead/AGM is fine especially if not depending on solar and perhaps instead keeping a charge from a water turbine from a river or stream. AGM have significantly less charge cycles than LiFePo4 and the disparity is growing more every year. China went both Sodium and LifePo4 due to logistical and shipping issues with some of the materials required in Li-ion. Li-ion batteries also have heating pads. I can't see AGM being viable in solar farms due to the low charge cycle ratings. Either that or whoever the manufacture is will be very happy as those batteries will have to be cycled out quickly.

I have 4 AGM batteries for a few of my inverters that need higher surge capacity in a smaller space and the UPS driver remembers me for it. Now they make me get the batteries out of their truck. Since I keep the AGM's fully charged with commercial power the charge cycles are less of an issue for me and thus the TCO/ROI is acceptable. LiFePo4 current ratings are catching up though. Now I can get one that has a 200+ Amp discharge rating and I am told there will be one with a 300AH/320 Amp discharge rating soon.

I am most curious about what comes next. The 3D printed solid state batteries look very interesting. 50% of the weight for the same capacity, higher C rating, significantly safer. Mass production is just starting for those so time will tell I guess.

not disagreeing with you either :)

The killer feature of lead acid designs is cost and availability. In many applications, they are significantly cheaper. The chance cycle issue is real and i’m glad you brought that up. For some applications, they make sense. One is a low power draw solar-powered website. Lead acid batteries also outlast most lithium chemistries by several years. These batteries have been around for decades now are are absolutely everywhere and the voltages are standardized. that alone is a significant advantage.

Case in point - i run a UPS using my old 12 V car battery. Granted, i cannot keep this indoors but it works well.

Similar to what you said - off-grid or backup power is the mainstay of lead acid designs. almost every electrical substation out there uses lead acid for backup power.

That hasn't really been true for years. At the same temperature, FePO4 outperforms lead acid in voltage, discharge current, and capacity.

> Operation below freezing ambient temperatures requires a heater and heaters need energy.

No. Charging requires a heater, discharging does not. It's really not reasonable to say "operation" requires a heater. While you're discharging, you're worried about the capacity and duration, and running a heater is a huge problem. The slower your discharge, the more of an issue it is to run a heater.

While you're charging, it usually isn't. You're already losing plenty of power to the charger inefficiency, it just takes a little more power to keep it above ambient. If you're plugged in it's irrelevant.

Fair point that only charging requires a heater but how does that meaningfully address the issue of cold weather operation? A battery requires charging and discharging and being able do to one but no the other won’t cut it, surely? The loss of capacity to heat is significant - often 10-30% capacity but that figure depends.

Also, i’m not sure plenty of power is lost to charging inefficiency. most industrial inverters operate at nearly 90% efficiency. Besides, above ambient isn’t a good metric - lithium chemistries do well around 10-25 C. If ambient is - 5 C, a delta of +5 C doesn’t change my core point.

Even if you are plugged in, lithium batteries aren’t dissipating heat. Not sure what the charger inefficiency has to do with this because that heat often isn’t the batteries themselves.

they're saying that when charging you likely have the spare current to warm up the batteries before you charge them.

> The loss of capacity to heat is significant - often 10-30% capacity but that figure depends.

But it isn't a loss of capacity (although there is also a loss of capacity due to cold, in any chemistry). The capacity is the same, it just takes more energy to put the same amount of energy in. If you are putting energy in, you usually have an oversupply, and heating the battery is not an issue.

> If ambient is - 5 C, a delta of +5 C doesn’t change my core point.

I used the phrase "above ambient" specifically because the battery does not need to be warm unless you need to charge it quickly. If it's above 0 Celsius, it can charge. The warmer you make it the faster you can charge it. If the wasted energy is an issue you can charge slower.

> most industrial inverters operate at nearly 90% efficiency.

An inverter is significantly simpler than a battery charger. FePO4 charging can start as low as 2.5 volts and go past 3.6 volts. Making a converter with a 50% swing in voltage is not particularly easy. This higher-end charger picked at random[1] drops to <75% efficiency at the end of charge.

[1]: https://www.analog.com/media/en/technical-documentation/data...

Nope. IIRC typical one is safe to discharge at -10 but needs to go to 0 to start charging.

I wonder whether there is some off-the-shelf controller that can do something clever like run a heater instead of charging battery till it gets up to temperature

There are some specialty ones that allow lower temps but that comes back to cost again

There are some batteries that integrate temp sensors and heating pads: losing some energy to bring the battery up to operating temperature.

Yeah one of the vendors I mentioned above sells batteries with exactly that functionality -- if the temperature is too low, the BMS disconnects and the heating circuit is powered by the incoming energy (whatever the source might be) until the cells are warm enough: https://www.canbat.com/product/12v-100ah-cold-weather-lithiu...

> unless you're going for the absolute cheapest possible build due to immediate budget constraints.

Or, you know, you get limitless amounts of 24Ah 12V SLABs free for the hauling away because they test at a bawhair under factory spec after five years of having an easy life.

I'm going to disagree with you, because decent deep-cycle lead-acid batteries can last very well, and they are very much cheaper than LiFePO4. https://youtube.com/watch?v=LPPUqLZOqCQ is the video that persuaded me, even if he does ramble on a bit.

LiFePO4 age by elapsed time more than cycle count, so after 10 years they will be reaching the end of their useful life regardless of how much you have used them. Lead-acid age by cycle count more than elapsed time, so you could have a battery last well longer than 10 years if you treat it well.

I'd note that lead-acid batteries are divided into deep-cycle batteries that have are designed for longevity and basic batteries that are optimised for peak supply current (for vehicle starter motors). Use a deep-cycle battery, otherwise yes it will die very quickly.

I'd argue that if you're in a part of the world that has unreliable sunlight, such that you want to store say 4 days of energy but rarely actually use it all, then lead-acid is a perfect fit, because you just buy lots of storage at a cheaper price than LiFePO4, and that regime automatically treats the batteries well.

If you're in a part of the world where sunlight is reliably every day and you only want to buy enough battery to last a single night, then I can see that LiFePO4 may be a better option. But I'd still be inclined to buy several days of lead-acid instead. If you want to charge your batteries from cheap early morning grid power and effectively cycle twice a day, then LiFePO4 is definitely the better option.

The other thing that is nice about lead-acid batteries is the recycling rate - they are very easily recyclable and very highly recycled. I don't think we're there with LiFePO4 yet.

Flooded lead acid needs to be topped up with distilled water, and shouldn't be kept near living quarters due to possible outgassing. If you run them dry, you will permanently damage the batteries. To recycle them, you have to drag them somewhere automotive. The premium you pay for LiFePO4 over lead acid is almost no maintenance and you can drop them off almost anywhere electronics are recycled to enter the recycling supply chain.

Batteries are going to improve rapidly over the next decade, and the battery you replace your current LiFePO4 with at end of life is likely to be much better when that time comes.

The video is ok for the spreadsheet-like comparison, but it claims that all batteries have "memory". Also claims that depth of discharge doesn't matter to lead acid (what happened to sulfation?).

One good point that was made is that lead acid starts to behave terribly after losing 20% of its capacity, to the point that they fail outright and can no longer hold a charge. Lithium can usually keep working way longer than that, just with a reduced runtime.

Those cycle life numbers look great, but lead acid batteries in practical applications tend not to last the lifespan advertised on brochures. We can gauge that by how confident the manufacturers are:

* The Trojan SIND 06 610 has a 2 year warranty.

* The NSB100FT - 3 years.

* The Battleborn BB10012: 10 years

The Trojan battery weights a whopping 220lbs and holds 600amp hours. It's not even in the same category as the other two. You need a minimum of two as they output 6v. The price for the amount of storage they provide is pretty good though.

> Lead-acid age by cycle count more than elapsed time, so you could have a battery last well longer than 10 years if you treat it well.

Have you ever seen a lead acid battery last this long? Was it able to hold a meaningful amount of charge?

Lead acid batteries may be cheaper but they are unlikely to survive for as long as claimed.

That said - if you want a battery backup that you basically never use, there is a chance that you'll get a good return on investment on deep cycle lead acid (specifically those industrial ones) – if they don't fail for whatever reason and are properly maintained. For the same amount of money you can buy a ridiculous amount of storage for a real emergency.

Good point about the recycle rate. Lithium is theoretically just as recyclable as lead acid, but the logistics are not there yet (but how will that look like in 10 years?).

About the video: This is the same guy that was crimping his cables with a vice and soldering them, with awful results. I bought a decent ‘crimping device’ for $30. I’ve seen his videos but I’m not buying it. Maybe OPzV stuff lasts 20 years but then you sacrifice a bedroom worth of floor space for a potentially dangerous maintenance burden that requires reinforcements of the floor. I’m exaggerating but still.

Second hand forklift batteries are a cheap source for lots of storage capacity. They tend to be deprecated well before the end of their service life simply because they can no longer make it to the end of a shift without recharging.

Do test the cells individually with an acid tester, a simple hydrometer one is easy to take along when you go shopping. One important thing to keep in mind when buying any kind of battery is that for some batteries there are pretty strict requirements as to how they can be installed, what kind of physical isolation you have to use and how you need to vent any gases that they produce. These rules can easily disqualify some battery chemistries or configurations from consideration.

> Although that sounds like a very light load, if you run it for 24 hours, it's equivalent to using 84 Watts continuously for one hour.

Its called 84 watt-hours and this is energy consumed in 24 hrs. 3.5 watts is energy consumption rate and is called as power(joules/sec). 84 Wh is not actually lot.

I made a calculator for raspberry pi energy consumption

https://tinyurl.com/nwu6sn4s

For a comparison, 50W doesn't seem like much, right? Maybe if you're older you had 50W incandescent light bulbs in your house. Normal thing.

Let's say a WISP wanted to run a very basic off grid relay site with some radios that are 8-12W DC load each and a router that's 15W. Total around 50W 24x7x365. ((50 x 24 x 31)) / 1000

That's 37.2 kWh per month.

You need a surprisingly large amount of solar panels to generate a reliable 45-50 kwH per month to refill a battery bank every day when the sun comes up, in November, December, January, February at latitude 45N or above. Like, really, a lot more than you might think. Four or more 370W 72-cell.

PVwatts says a 4-module array of 370w panels, including AC losses, will produce about 100kWh in January at 45N FWIW

That's assuming perfect sun exposure on a roof or ground moving with no shadowing at any time of the day and at the optimal tilt.

Pvwatts says that usable energy from a 1480W system at 43.6N in Boise ID might be more like 77kWh a month in December, the shortest sunlight month of the year.

An off grid system generally needs to be calculated to survive December. January will be a few percent better as days start getting longer.

Realistically, to get through entire week long periods of snow and overcast, if I had a load that was 50kWh a month I would want a 75-80kWh a month predicted PV production system to make it worry free in December.

Going against the trend here but I still use incandescent bulbs in key places like my desk and so on. I find LED to give a terrible light (not the whole spectrum), but they are getting harder and harder to find.

Incandescent bulbs are not full spectrum, though. They are on the warm end of the color temperature scale, much more "orange" than mid-day sunlight.

The good news is that you can get LED bulbs in any color temperature you like. My house is full of "warm white" LED bulbs and I could not tell any difference in brightness or color when I swapped them in for incandescent many years ago.

The difference is colour rendering and the nature of the spectrum.

An incandescent bulb is, by definition, emitting black body radiation - it’s a nice curve encompassing a good chunk of the spectrum, but as you say biased towards the red end.

LEDs tend to emit discrete quantised frequencies of light, as a result both of the dopants in the LEDs and the phosphors used on bulbs.

They have got better, due to better phosphors, but they still don’t render colour as well as incandescent bulbs.

That said, I’m all LED here as I cannot afford within our energy budget to burn a kilowatt or more on lighting.

They are continuous black body spectrum which we got used to

> LED to give a terrible light

Let's stop spreading this myth. Cheap LED lights can have terrible spectrum. Good LED lights have a better spectrum than incandescent.

I should have phrased it differently. See madaxe's comment:

> The difference is colour rendering and the nature of the spectrum.

If you compare it with your own eyes, you should definitely be able to see it.

Here's a good article explaining in-depth how and why LED light looks different from incandescent.

https://nymag.com/strategist/article/led-light-bulbs-investi...

> If you compare it with your own eyes, you should definitely be able to see it.

People buy cheap LEDs and then say this. Buy good quality LED bulbs and you will see no difference.

There are a few specialty LED lightbulbs made with (old-fashioned) yellow glass that offer a warm (yellowish depending on the room) and comfortable light.

Finding LED that have light that doesn't look bad is unnecessarily complicated sadly

But 84Wh is still enough energy to drive a modern battery-electric vehicle around 500 meters. Kind of puts things into perspective.

I find these numbers really fascinating because it shows how efficient battery-electric vehicles are, especially when you think about things like incandescent bulbs, which easily will run at 50W just to light up a small room.

Don't get me started on cars that display usage in kWh/h per 100km. Yes, you read that right.

Conversely, it shows how sparse kinetic energy is, and that's a good explanation to tell people that would see storage issues solved by damming every stream.

> Don't get me started on cars that display usage in kWh/h per 100km. Yes, you read that right.

ICEs use litres per 100km which I think is where this comes from. And I hate it. miles-per-gallon is much easier to understand I think. I wish we could have split the difference in the EU and just had km-per-litre. I'd rather know how far a tank will get me than how much fuel I'll use to travel exactly 100km

The biggest problem with MPG is its inverse nature makes it a bad unit to use to compare cars.

A 20 MPG car is not twice as efficient as a 10 MPG car.

http://www.mpgillusion.com/p/what-is-mpg-illusion.html

L/100km has the length and volume units reversed, which allows comparisons.

A 20MPG (11.76 l/100km) car is twice as efficient as a 10MPG (23.52 l/100km) car though?

The issue is going from 30 to 20MPG is not the same change as going from 20 to 10MPG, where as the difference between 15 and 10, and 10 and 5 l/100km is the same absolute change.

I might be hung up on the word "illusion". The only difference between miles per gallon and gallons per mile is that the former increases and the latter decreases with efficiency. They are still saying the exact same thing.

"They are still saying the exact same thing."

They are but now I prefer .05 GPM to 20 MPG.

I do as well.

Everyone in the US it seems to like bigger numbers. Just look at the argument some people use to why some people prefer Fahrenheit over Celsius.

... is what I would say, but Tesla seems to be the only one using the sensible Wh/m or Wh/km. All the German ones use the nonsensical kWh/h per 100km.

In fairness, 0 being cold and 100 being hot is pretty intuitive. I would be curious to know how people raised on Celsius feel about Fahrenheit after having lived with it long-term.

> A 20 MPG car is not twice as efficient as a 10 MPG car.

Why not?

The page you linked doesn't talk about "twice as efficient", it talks about an absolute number of gallons saved per distance travelled.

Also, assuming there was no typo, vegardx's point was that "kWh/h per 100km" is invalid. "kWh/h" is the same as "kW", and "kW per 100km" (power per distance) is not describing vehicle efficiency, it's non-sensible. "kWh per 100km" (energy per distance) is.

> And I hate it. miles-per-gallon is much easier to understand I think.

It's just something you're used to.

> I'd rather know how far a tank will get me than how much fuel I'll use to travel exactly 100km

Well, there you go, you're comparing apples to oranges. Unless your tank is exactly one gallon, you've made a conversion when you compute how far a tank will get you. Well, we do the same thing here. I want to travel 500 km? I'll multiply my L/100km by 5 and get how much gas I need. This tells me how many times I'll have to refuel, etc.

true I guess. maybe its just something I'm used to. distance-per-fuel-amount just seems intuitively more useful to me than fuel-amount-per-distance, even if they're two sides to the same coin

I think it'd be incredibly valuable if all vehicles could pick one common unit. Personally I think that need dominates all others. And it suggests to me MPGe is the way to go in the states, to the extend that it makes me want EV "fuel" gauges to be "gallon-equivalents" (33.7kWh). Yes your car only has 2~3 gallons of gas capacity, that's because it's badass & efficient. This is of course (imo: alas) never going to happen.

I think the actual units used in EU are, for example, 19kWh/100km (from the BMW iX which does very well for it's size-class). You seem to have an extra /h in your figure. It has the advantage of being a understandable number, relatively well sized in scope. People can think of 100km as a reasonable length in their head that connects distant points. We tend to think in terms of kWh, which is what electricity is typically metered in world wide. It feels like a poor use of a metric system that shouldn't have a bunch of weird prefixes (there's a k above & below the divisor? are you kidding me? 100km? c'mon!!) but the units are people-sized, are things we can work with in our head. And the final number, 19, as in 19 kWh/100km, is reasonably scoped, going up if you're more efficient, going down if you're less efficient.

It's inverse from MPG, putting the range-unit is on the bottom & the energy-unit is on the top. Some people love it: they claim that the difference between like 12 & 24 MPG is hard to appreciate the savings off of, whereas the difference between 24 & 48 MPG looks big but is actually only half as much fuel saved. Personally, I don't really chalk this up as a win, but some people think it's important & I can recognize that potentially it might be helpful.

I still think we should just use 33.7kWh / 1 gallon-of-gas equivalent as the common unit of energy & give everyone a common frame of reference.

Some German cars display current usage as kWh/h, which is just a stupid way of saying kW. If you're using 3kW for one hour, that means you're using 3kWh ... per hour. It just doesn't make any sense to write it like that. They correctly display the average usage over a given distance as kWh/100km.

There's a lot of fuzz in the EV space since everyone is advertising WLTP (previously NADC) numbers as an indicator for range. It uses a standardized test, so this means the numbers should be comparable. But they're not. Some BEVs are much more efficient in cold weather than others, due to things like heat pumps or just better engineering, like aerodynamics. This isn't well reflected in WLTP, and people get disappointed.

You can easily argue for both kWh or Wh. I've always been a proponent of using the smallest units possible, since then everything is just addition, regardless of what you want. With everything being in units of 10, it's fairly easy to do, either way. You could argue that the logical conclusion would be to use Ws/m, which is just ... Joules/m, another SI unit. But then we're using units that most people have no fundamental understanding of.

It would be worthy sacrifice to get rid of miles.

Now let's talk about wheel size. mm/percentage/inches all in one unit...

84 Wh is enough to propel a human on a bicycle about 20 km in about one hour. From this perspective electric cars are ludicrously inefficient ways to get around. Maybe in the future we'll view car dependency as similarly wasteful to using incandescent bulbs everywhere.

Bicycles are something like 99% efficient though so anything will look ludicrously inefficient compared to them.

Have you cycled in the rain or snow? If yes how many times?

Periodically I see colleagues trying to come at work by bicycle. The longest lasting record is one and half year. All the others didn't last after the summer.

Fwiw it would take me 1h of walking to go to work or about 1h20 if I take a couple buses. Or I can take the car and be done in less than 10 minutes.

This is less about the winter and more about the lack of appropriate biking infrastructure. [0]

[0]: Why Canadians Can't Bike in the Winter, but Finnish people can: https://www.youtube.com/watch?v=Uhx-26GfCBU

I think it's mostly about culture and infrastructure. When we lived in Southern Germany, I cycled to work literally 5 days a week for three years (22-25 km per day, depending on the route), yes also when was snowing or raining. I still use cycling as the only means of transportation to the office, but with WFH it's currently only 2-3 days per week. I live in The Netherlands again, where cycling is one of the primary forms of transportation.

Rain: I use rain pants and waterproof jacket/shoes. Snow: bike lanes are cleared, though I did regularly cycle on snowy roads in Germany when they were not cleared yet. Tires with some profile and experience make it very doable.

Honestly, I was with you on the weather aspect. I do go to work daily, rain or shine ... it sucks to drive in the rain and I was lucky to go full HO during a bad winter, but overall it's perfect workable (in central Germany).

But then you wrote that you walk just 1h to work ... That can't be more than 20 minutes by bike. (My commute is 30 minutes by foot, 15 by car, 1:30h public transport... But due to the road layout it takes me just 10 minutes on average by bike.)

I drove to work for 10 years, although I did skip winter season, riving on ice is NOT fun

> Fwiw it would take me 1h of walking to go to work or about 1h20 if I take a couple buses. Or I can take the car and be done in less than 10 minutes.

That's kinda the problem. Even here with pretty good infrastructure car is 50 minutes in peak traffic, metro + walk to metro station + few stops of tram is 1h. If I go like 2h after peak it's 35 minutes...

But how many parsecs does it take to do a Kessel run?

Agree it doesn't feel like a lot. We run our house, including a decent sized pool pump, off solar for most of the day. A Pi seems like very small fry in the scheme of things.

Getting something like this up and running in a few short hours of Dutch summer sun just shows that everyone should be trying it (that includes me).

I am less of a DIYer than the author and safety was always a priority... good author knows about amps, cable sizes, etc.

But charging lead acid battery inside a house? I've stumbled across warnings where it says they must be charged in a well ventilated area. Anyone care to chime in, for the safety of author? https://www.ccohs.ca/oshanswers/safety_haz/battery-charging.....

Sealed lead acid (SLA) batteries only outgas an appreciable amount when overcharged/overdischared. Vented instead of sealed types can also be used indoors but require their own ventilation system. The majority of UPS systems use SLA batteries indoors.

As long as you don't keep the battery in an airtight container you're generally good (vents on the battery container, room has ventilation)

But is it safe to inhale the gases?

Its Hydrogen, the concern is explosion https://www.ccohs.ca/oshanswers/safety_haz/battery-charging....

> Overcharging a lead acid battery can also lead to the generation of hydrogen sulfide, which can cause harm to workers if exposed.

The concern is also the toxicity of H2S. Most SLA chargers are poorly designed and will overcharge any battery that isn't in mint condition.

Agreed that cheap "trickle" chargers with unregulated voltage can cause overcharging if left on for too long (days to weeks on larger batteries, as their current is usually under 1A)

Better to invest in a "float" charger with a regulated output and automatic shutoff. As with many subjects, if you go the cheapest route you pay with time or safety risk.

For those thinking about replicating this: Victron is really popular because it's extendable and the management interface is reasonably open, but the zoo of required devices makes the costs explode quickly.

Maybe look at Deye instead. I'm running a 12kW unit (they're available smaller) with a 48V battery. The software is in poorly translated to English, firmware updates are made by the manufacturer remote on request and it has no shadow management (meaning it might end up on a local maximum in the MPPT, not the global maximum) - but the unit cost me about 3000€ with 10yr warranty instead of the >7000€ for an equivalent zoo of Victron parts.

Of course it can do black starts from PV or battery, and act as a UPS on a secondary output. Pulling data locally can be done using a RS485 modbus interface; so I open my firewall only for firmware updates.

The 3.6kW single phase unit (SG05LP1) can be had for less than 1300€. A 5kW three phase unit is only a little bit more expensive, but I'd worry about standby consumption in low power scenarios with only a few modules (mine hogs 80W, but a three phase Victron setup does so as well). These are string inverters, so you need more modules for them to reach their start up voltage, and then some more to put them into the MPPT zone. The 1 phase starts at 125V and the MPPT tracker works with 150-425V, the 3 phase units 160V & 200-650V respectively. When I browsed the market there were other offerings from other brands with 90V start up; but be careful to get a unit that's legal to connect to the grid IF you want to have grid fall back (here in Germany, Victron and Deye are legal - at least the parts I looked at. But you will always need a electrician with a concession to register them with the grid company. Some people don't care and just setup their systems though).

Important: The voltages depend on the chosen PV module; mine are in the 40V per module ballpark, but iirc I might maybe have seen up to 60V? So for the 3.6kW unit you'd want at least 3 or 4 modules.

Not sure what zoo of parts you’re referring to? I have two multiplus 5kva 48v, a bmv-712, a venus gx, and a pair of their biggest MPPTs - and for our pretty large install it shook out at about €4,500. Without the redundancy, it would have been more like €2,500.

Don't get me wrong, the Victron systems are nice & I envy their great traits I've praised in sibling comments. But your system doesn't compare on the power specs.

There is no exact equivalent for the Deye with Victron. The Deye can do 15.6kWp solar, split over 2 MPPT. The topology is such that one MPPT can do 15kW while the other does 0W (I did not believe this, but I've talked to the manufacturer and it's indeed correct). The inverter can output 12kW AC, or draw that much for charging the battery. If your load is not balanced well, there is a video of someone testing it with 12kW sustained output on a single phase (this is only useful for a select few maniacs though; I'm not one of these). And if the 12kW is not enough, you can put them in parallel (like with Victron).

I deleted my notes on the Victron setup, but this is something similar to what I was looking at (about Sept 2022): 3x Multiplus 48/5000 on the AC/DC end for full three phase setup (back then 1700€ each, now 1300€) - mind those can really "only" push 5000VA or 4000W at 25degC. Our roof would be 1x MPPT RS 450/200 (pretty stable at 1800€), the string in the garden 1x 450/100 (1200€ in Sept, 1000€ now). A RPi plus USB adapters and PSU and sturdy case for VenusOS (or a GX unit) would be close to 100€ extra, also add additional cables and the necessary busbars (dunno, 200€?).

For a three phase that's 7000€ today, or 8400€ in September. Of course that's just one way of building a system, and Victron is amazingly flexible - and with my 14kWh battery two multiplus would probably have been enough (caveat emptor: no idea if my grid operator would have accepted 2x5kVA or rejected it due to the inbalance).

Lots of people use a SmartShunt or Lynx, these also add to the costs of a Victron system.

Why zoo: The footprint of the Victron 3x MP and 2x MPPTs is nearly 0.9m²; add busbars and other periphals, and you're easily at 1m². Plus, each device needs some clearance due to the heat. The Deye is one unit with 0.3m² footprint. This is also nice.

Ok, you’ve got me interested - thanks for the write-up - now I just need to see if it can coexist with the victron ecosystem I already have. Probably.

Victron is good stuff and it is made to last. They're a big supplier to maritime integrators to provide power on board of ships of all shapes & sizes. I've yet to see a Victron inverter fail before the end of the lifetime of the installation it was a part of whereas most other inverters including Xantrex and ABB tend to die after a decade or so. Which isn't bad but still it can be a big hassle to replace an inverter if the form factor has changed.

Also: consider decoupling your battery charger setup from the solar portion, this will give you a lot more flexibility in terms of siting (you can then place your battery and charger where you want on your local installation). You can use HA to bring your battery online when it is most needed and even when to charge it based on the outputs of multiple fields of solar, an integrated solution really only works with a single inverter or a set of inverters of a single brand.

And if you can stay away from stuff that requires an internet connection to some manufacturer, not all upgrades are positives and your data shouldn't be going there anywhere. Also it probably isn't a good idea to hand over control of a grid connected device to another party, especially when that device has firmware that can't be audited.

> consider decoupling your battery charger setup from the solar portion

Can you provide more details on this? I’m having a hard time imagining how the solar, inverter, and battery chargers are connected in relation to the house and grid.

And what is HA? Thank you.

HA -> Home Assistant

If you have a separate charger/inverter that you can control remotely using HA then you simply monitor your outgoing power and if that goes negative and your batteries aren't charged yet you instruct the charger portion to charge the batteries. Then, when the sun goes down you can order the inverter part to come to life and supply current up to the point where the outgoing current is close to zero. Like that you maximize your own usage. And by having this split up you can site your batteries in a spot where the temperature is relatively stable, but still outside of the house which is usually not where you have your solar panels.

A solar inverter should be sited relatively close to the panels to avoid cable losses and to reduce the risk of having unfused 800V DC cabling running through your house for any appreciable length. Ideally you want those cables to be just long enough to get under the roof to the spot where the inverter sits and then regular cabling to the distribution panel.

By connecting the charger/inverter combination to the distribution panel in the same manner you get a lot more freedom. And if you have multiple sets of solar panels that's really the only setup that makes sense otherwise only a limited number of panels can be used to charge the battery (the ones that are directly connected to the inverter that feeds that battery). That's why I'm not a huge fan of the so called 'hybrid' inverters. They make a lot of assumptions about the physical layout of the location that may not hold true in practice.

Here I have 50 panels divided into five fields, 6,8,8,10, and 18 panels in each of them and three inverters. This gave a lot of flexibility in where panels could be located. But if I want to charge a battery in a hybrid setup I'd have to pick which set of panels to use and then I'd still be limited in where I could locate the batteries, presumably they'd be close to whichever set of panels I would like to use to charge them with.

But by decoupling that and using the AC network as the bus I can put them pretty much anywhere that I can reach with another cable run into the distribution panel. That way all 50 panels can contribute to the charging.

An interesting extra option is to run one more cable from the battery charger/inverter to the inverter port, that allows you to power a set of critical loads from battery power. But since the grid here is very reliable I won't be using that.

hth, feel free to ask more.

I haven't heard of a setup like this before. It seems like you would be loosing a lot of efficiency having to translate the voltage to AC and back to DC to charge your batteries.

Not really, those inverters are 96-98% efficient.

Ah, a jacquesm reply, I feel honored :)

Of course you're right, the Victron are good, and they're proven. They're incredible flexible and for hackers like us they're amazing units.

But for me the Deye was 2500€ shipped (group order with the german tax break applied), with 10yr warranty and a local company acting as a liason for warranty claims. If the Victron setup would have been 3000 or maybe even 3500€ I wouldn't have looked at the Deye - but we're currently energetically renovating a house, and with the current price hikes we have to be careful not to drain our funds before we're done. So for me the choice was a smaller system (both kWp and kWh), or the Deye.

Since I can locally control the unit via RS485 (I use HA and node-red), I'll eventually do a lot of sheningans as well. I despise things that require cloud and the Deyes cloud connection is no different (and hence severed in the OpnSense). If people want to consume most of the generated power onsite good local control is a necessity. Once we have other things like the central heating and the new roof done and when I'm not busy with plaster work around the new windows anymore, maybe then I'll setup the more advanced energy managment like evcc or custom automations. Until then the 14kWh battery takes care of ensuring energy stays local (and I only make sure not to charge the PHEV battery from it by accident - the Deye happens to have a suitable output port that's activated if the battery is full; I have yet to wire that port though).

Anyway, for someone who has the liquidity, and feels they want to use the Victron ecosystem, by all means, for lots of metrics it's better than the Deye; but for me I didn't see that the Victron would save me more money than the initial invest. Also, the single Deye happens to fit my requirements pretty well (it's a bit more powerful than necessary, but the extra costs over their smaller units were neglibible).

It's all trade-offs. I have a pretty weird setup with lots of gear that gets switched in and out according to power availability, and inverters in different spots (two in the garage and one in the attic). I still haven't installed a battery because we - for the moment - have 100% net metering here so it would be a waste of money. TCO is one way to look at things, installation flexibility another and finally of course initial outlay: better to buy the setup you can afford than to drool over a better one that you can't.

I've yet to come across Deye in the wild so nice to have some data points. What I'm really curious about is to what degree the various setpoints are configurable. I have a Growatt here that is giving me a ton of trouble and two Solax units that have been rock solid since first installation (and without any configuration at all). All of them offline.

On the panel side here I have a bunch of AEG branded glass/glass panels (AEG has licensed their brand so these aren't actually made by AEG but they are made in Germany and look to be well constructed and with a 25 year predicted life span I think I'll be long gone before the panels will die).

I'd love to hear how you are faring with all of the stuff that you've done.

I have it running in a testing setup for about 2 weeks now. 8 modules flat on the lawn (Maysun glass/glass 410Wp), the battery connected and tied to the grid with export power limited to 0 because my meter is ancient enough to spin in reverse (which is illegal to do here).

Which setpoints do you mean? I'm not familiar with all the terms, especially when they vary by manufacturer.

If you mean the power limit the Deye should put on the DC bar (i.e. put into the battery), that works reasonably well. If it's at 100% it will still charge a few Watts, but nothing severe.

The other meaning I could come up is the target power to draw from the grid when export is disabled (as in my case, for now), or when it is feeding energy from the battery into the house when I draw more than the PV array delivers. That's 20W by default, but can be user configured. This fluctuates somewhat strongly, but overall works out correct. I believe the reason isn't the software, but the poorly routed measurement cables: It uses measuring transfomers and the cables in my setup go tightly and parallel to the power line that connects the inverter to the grid. The electrician said that's not an issue, but I guess he usually measures 50A+, in that case the noise is negligble. Around the 0A point the noise has a much bigger impact. But that's easily fixed. Eventually I'll use that option to prevent the battery from discharging when the car is charging over night (e.g. when I charge with 1200W, I plan to set the target to that value).

I'm not sure if I can configure other setpoints, e.g. the MPPT target voltage (which would be a nice trick to get shadow managment). I can define some other things like "from $x a.m. to $y p.m., keep the battery at $z%, grid charging is [not] allowed, powering on the external generator is [not] allowed". For testing the battery balancing (it has an additional Neey active balancer) I used that. And yeah, it can trigger an external 3phase generator to power up (not sure if the 1ph can do that).

As far as I could find, all options are exposed via RS485. I adjusted the sunsynk HA addon to work with the newer 3 phase inverters (sunsynk = deye rebrand; changes are already merged upstream). Only thing that I'm missing is the current limit set by the BMS, as well as other BMS data sent to the inverter (I did not search the published register map for that, yet).

What I can already say:

All in all the technical side is pretty nice; as said in a sibling comment, I could theoretically push out 12kW AC on a single phase if my local load is severly inbalanced. And the MPPTs are pretty flexible in how much power they can accept (as long as the sum is less than 15.6kW at all times).

What's horrible is the UI side. Some phrases are highly unclear, and requires knowledge of what the option actually does. E.g. "signal island mode" means "in case of grid failure, tie neutral to PE on the UPS output". In German installations that's always necessary, else RCDs will be much less effective. They would benefit greatly if they had a team of knowledgable translators.

Having to ask their support to do an update is also a joke; especially since they don't publish release notes. Also, the update power cycles the inverter, which causes the UPS output to lose power.

My 14.3kWh LFP battery has a 200A Seplos BMS. The inverter and the battery talk via CAN. In the BMS the power limit is set to x Amps. But the inverter shows a limit of (x/2) Amps. Now my battery should eventually operate a 140A continuous, but I'm not feeling to well about setting the limit to 280A and one sunny day having the two systems decide to get along and actually push 240A (the Deye's limit) over the connection+BMS sized for "only" 200A. The solution is to get another BMS, but back when we formed the respective group orders, people didn't yet know of this incompatibility. Plus we were focused on Seplos because the Victron users felt it was imporant to get a BMS that would not disconnect the negative bus.

Still, for someone looking at a small plant with just a few panels and a small battery, it's a great value preposition. Especially when paired with a different battery/BMS. With the 8 modules behind the house (shadowed in the morning and the late evening) I had 105kWh PV and 120kWh grid power over the last two weeks. That's 1k€ for the modules, 1.3k€ for the smaller 1phase 3.6kW inverter, 1.2k€ for the 3kWh Pylontech US3000C, plus some cables and AC fuses for 200€, plus a DC fuse+SPD box (<100€ if DIY) = 3.8k€ for basic stuff. What's missing is panel mounting (800€?) and, depending on local laws, an electrician to sign off on everything.

12KW on a single phase is really not what you want to do though, that works out to 50A which is likely more than your distribution panel is wired for, usually they are good up to 40A and 50A for a couple of seconds but more than that and you are inviting blowing up the utility side fuses. You will also need pretty beefy cable to be able to run that kind of current, 6 mm^2 ~30A, 10 mm^2 ~40 and 16 mm^2 ~55. Unless you want to run your cable really hot, which I would not recommend. Also, you will have to beef up the wiring in your distribution panel, the utility side fuse (which normally is 3x25 or 3x35, rarely 3x50 though it is possible but will require fatter bus bars and special breakers as well). Much better to divide the power over your phases. That way you can run 12KW on 3x2.5 mm^2.

The setpoints I am struggling with are the difference between for instance the voltage at the inverter versus the voltage at the distribution panel, when pushing a mere 5KW into the grid from the upstairs inverter that raises the voltage enough that the inverter will trip. This is not due to the usual suspects (faulty wiring, loose contacts) but simply because of the length of the feedline to the attic and the fact that it is 2.5 mm square tri phase cabling, which has a 4V voltage drop over that length and there is absolutely no way to compensate for that.

Highly frustrating. Other interesting set points would be to be able to de-rate the inverter and to be able to get it to shut down faster once the sun has gone under.

That's really good value for the money what you've got there. My setup is a bit more expensive than yours but it also makes a lot more power (as it should :) ), I've spent a lot of time on getting it all set up properly for the summer. The biggest problem remaining (and that I won't be able to fix) is that I can't angle the panels on the low roof properly because that would upset my neighbors so they are at a very shallow angle, just enough to the get the water to run off them but even then at the edge of the panels in the 'down' direction there is a little area of about 5 cm where water pools long enough for algae to grow. So I will have to clean these quite frequently. Maybe I'll figure out a way to deal with that but so far nothing that really worked well. A steeper angle would require a higher starting point or a lower ending point, neither of which are feasible.

The real pay-off is in March/April and September/October when we will save substantially on gas by heating using an air/air heatpump with a COP of about 3 to 3.5 at the temperatures at that time of the year. That should put a sizeable dent in the energy costs.

Dead thread comment: I just scored a 17 KW Solax inverter on the local ebay equivalent for $500, 4 strings, 2 MPPT, super happy :)

Cool project. I think we really need some free software sensor/controller libraries/frameworks for solar setups.

The reason is that here in Germany, and presumably elsewhere in Europe, these "balcony powerplants" are taking off. You are allowed to plug up to 600W (soon up to 800W) into your socket without further trouble.

But unfortunately, most people will waste a lot of energy this way. Very few people will have permanent usage of 100W or more. Instead, consumers like refrigerators will turn on and off multiple times per hour.

So the ideal setup would consist of one or more load-measuring sensors, a smallish long-lasting battery (LiFe?), some oversized panels (say up to 2kW) and a converter that hooks everything up.

The controller should ensure that you feed power into your grid only when you need it and otherwise charge your battery. I think that such a setup could easily get you 4kWh/day of consumption in spring and summer. And potentially still 1kWh during most winter days.

It's not wasted energy. The country (perhaps even the continent) still benefits from it by having to burn less gas and coal

With regards to the wasted energy that is potentially made by the panel but unused, that doesn't offset any other power production since the power wasn't going to be used anyway

Of course the power is used. It's in the grid, and every power source has to be compensated by a power sink, otherwise you have instable grid = blackout if the deviation is too big

Are you assuming the panels are grid-tied? I may have missed that in the article, the setup sounded very off-grid to me at which point the power potential is lost if not used immediately.

Balcony powerplants (see comment I responded to) are connected to the grid and offset self consumption by their production

Are there actually inert (non-flammable) batteries that have a decent energy density for this? I would be worried about having any kind of sizeable lithium battery in an apartment, considering even laptop-sized batteries have enough firepower in them (but at least that one can more or less be picked up and thrown out the window in an emergency).

LiFePo4 batteries are very safe and do not have the thermal runaway problem that LiPo batteries do when they are damaged due to improper charging, abuse, or manufacturing defect.

As long as you stay away from the prismatic ones. If you do use those make sure you only use a properly designed enclosure to contain the forces exerted by the batteries as their charge, there is a reason manufacturers quote battery capacity at 300 or 500 kg clamping force. These are not at all easy to work with.

What would be the consequences of non-containment? Do those batteries swell and completely fall apart or do they just move a bit (if so, flexible cables and leaving decent room for expansion should be enough)? Do they merely need the compression to achieve the rated energy densities, or do they fail dangerously because of insufficient compression?

They can fail dangerously because the deformation can cause the busbars to become dislodged. Definitely not just a capacity thing.

Not sure if you saw but there's a great little German startup called "We Do Solar" who produce solar panels specifically for use on Balconies. My house has a flat roof and we'll be putting solar up there in the near future but I also plan to get panels for the balcony on our second floor as it runs the full width of the house and should add quite a chunk of generation capacity (downside is it's west facing so will only really provide power from the afternoon until the sun goes down).

The other problem is the 3.5 watt draw, or 600ma at idle, of the PI4B.

If you used a PI Zero with an ethernet expansion board this goes down to 100ma at idle. 6x less. You still get 1ghz cpu and 512mb of ram. I could even run django and postgres on that.

Certainly you don't need gigabytes of ram to run the blog. :)

The Raspberry 2 (original ARMv7 not underclocked Raspberry 3 ARMv8) is the best low power server. 1W idle and 2W 100% (6x more perf. than Raspberry 1 = Zero with Eth.).

They saturate the SD card SPI almost to the byte/second.

32-bit is enough forever, specially when you only have 1GB, but I'm staying on 32-bit on my 8GB RPi 4 too, because 4GB per process is enough when you also need the OS to have ample RAM.

If you are lucky enough to have some ARMv7 RPi 2 and/or Rpi 4 8GB, they will be priceless for eternity.

The RPi 2 is the unpopular kid of the familly, I don't know why. Maybe it got erased pretty quickly by the Pi3 performances and Wifi capabilities.

The thing I don't understand tho, is why they didn't chose this Soc for the Pi Zero original, instead of using the already decade-old ArmV6 CPU.

They can't, the RAM was external which wouldn't fit on the one sided Zero.

Thus why they bounded the 512MB ram in the package for Zero 2.

Physical limits are now everything you'll see until the end of time.

8GB is the largest RAM you will ever get in one chip.

1TB is the largest Micro SD.

Etc.

A Pi Zero can go down to 0.5W idle. The Pi Zero 2W should also be good, but is very hard to obtain right now.

The original BCM2837 was a terrible chip because the cooling is of old style so the PCB can't transport enough heat away and the package was plastic insulating from an eventual heat-sink. The Pi 3+ and 4 changed that.

BCM2836 is the real deal, peak SoC for non GPU + SD card duty:

https://wikimovel.com/index.php/Broadcom_BCM2836

https://en.wikipedia.org/wiki/ARM_Cortex-A7

> 32-bit is enough forever, specially when you only have 1GB, but I'm staying on 32-bit on my 8GB RPi 4 too, because 4GB per process is enough when you also need the OS to have ample RAM.

I thought 32-bit limited the entire system to 4GB of memory (all processes + kernel), not just per process?

That wasn't really true with PAE: https://en.wikipedia.org/wiki/Physical_Address_Extension Well that's the x86 extension, ARM has a similar extension called Large Physical Address Extension.

As mentioned in that article, Windows limited it to 4GB if you weren't running Server Enterprise, but Linux generally has it enabled by default.

Correct. Pretty much any raspberry is not a good choice here.

Did you ever work out how much energy was expended to manufacture and transport the parts? Chances are that with solar panels facing west in a place like The Netherlands, it will take a long time to come out on top with your carbon footprint.

I reckon that the most energy-efficient setup for your blog would be a hosted solution. Data centres are already optimised for low energy use. And some cloud providers have committed to become carbon neutral.

Lowering your overall household electricity use would be a more effective way to lower your carbon output.

I also think that this setup will not be worth it ecologically or economically.

And I bet his hardware saturation is low too, making it an even worse use of resources compared to shared hosting in a data center that uses bin packing or live migrating VMs or whatever. Because in the end you care about resources used for the actual work done, not the work capacity of the hardware.

While it doesn't make much difference at this scale and it is a valid experiment to learn about solar power, it is telling of the general view about energy and environmental impact. People equate solar or wind or electric vehicles with green when the devil is always in the details.

Did you read the article? Quote:

> It's fair to say that my experiment isn't rational because of the sub-optimal solar conditions. Yet, I'm unreasonably obsessed by solar power and I wanted to make it work, even if it didn't make sense from an economic or environmental perspective2.

This is just a fun experiment

> If you ever intend to build some kind of solar setup yourself, consider a 24 Volt or ideally an 48 Volt system to reduce currents and thus save on cabling cost.

I sort of regret going with a 48V system because it prevents me from plugging in a lot of devices directly to the battery. I have a few USB-C PD fast charging modules I would want to use directly. Also a battery-to-battery charger such as an iCharger or ISDT product won't do 48V as input or output. Not a big deal if you just want to connect an inverter all the time.

A more relevant issue may be that your solar panel's voltage will have to be > 48V. Actual voltage will depend on your MPPT charger. Victron seems to require battery voltage + 5V. Mine requires a minimal of 60V from the panels, so I have 3 24V panels wired in series, and cannot downsize.

I think 24V would've been a good sweet spot. The USB-C PD modules only step-down, so they cannot output 19V with 12V power.

For off-grid setups (which I consider the OP's setup) I would also consider 24V. I would consider ElectroDacus [0] which would replace the need for an MPPT and a BMS for lithium batteries. So besides a panel, battery and inverter this is all you need.

[0] - https://electrodacus.com/

> I sort of regret going with a 48V system because it prevents me from plugging in a lot of devices directly to the battery

I think there are plenty of 48->12 volt DC-DC converters that will alleviate this issue.

You can still have a 12-volt bus, but since you're not plugging directly into the battery you'll suffer some conversion losses (buck converters are generally 80 to 95 percent efficient, depending on the operating conditions and cost)

Hey peeps.

Sorry for hijacking the topic. I also live in the Netherlands and my backyard perfecty faces south, which means i get huge sunlight on that side of the house. But because my house has a glass-roofed extension on the ground floor, all solar companies i spoke say they can’t install panels on the roof because they can’t build scaffold on that side.

Here’s an image to explain a bit better. [image](https://imgur.com/a/WE1Qojf) So the red area is the glass-roofed extension on the ground floor. And blue area is the space on the roof that solar panels should be placed. Green is a dormer (which they said they can’t also put panels on top)

I was wondering any dutchies might know a solution/advice a company about this? Also is there any portable panels that i can put on top of the glass extension?

Thanks

I replied about this on another comment but have a look at "We Do Solar" their product is designed for installing on balconies but I guess there is nothing to stop you installing it where ever you like! (You might just need to add a bit of a frame to support them?)

Beware, those tend to be ballasted, for mounting on a light roofing structure you really want something that isn't ballasted.

not in NL but my parents have the same problem - glass roofed extension stops the installation

I dont understand why they can't just access the roof from the other side, climb over the apex and down. They walk all around on the roof once they're up there, does it really matter which side they climb?

It isn't clear from the picture and I guess it's too obvious, but if you have a neighbour, they can climb from their roof. That's how my neighbour got his installation done.

I have seen them do more complicated installations (4 floors scaffolding + crane to lift panels), I don't know why they refuse that one.

Hi, fellow Dutchie here. I've just built something quite similar and I took a bit of a shortcut: I've used the panels as the roofing. This was a bit tricky to do properly but now that it's done it looks gorgeous and works quite well. Drop me an email if you want pictures or if you want to come look at the setup in person. It's 18 panels, 3 'long' and 6 'wide' for a total of a bit over 32 square meters.

It seems that a major cost of solar installations is the inverter. Power electronics that generate >100W AC power are big and expensive.

Now that more and more devices use USB-C PD for power, I wonder whether it would be possible to forego the AC inverter, and just power everything with small USB-C power supplies that have 12V input and can be powered directly from the battery.

Or maybe you could use a 110V inverter instead of a 230V inverter? Switched mode power supplies usually accept either.

yes - my small inverter was 30EUR - its only capable of delivering about 180W. That was a significant portion of the total system cost for my toy system (with a 180W panel).

Yeah, inverters are pretty inefficient too. I've got a 12v battery and I power some stuff directly, and then a couple things from a 12v->5v buck converter. So far so good, even though the applications are limited. My setup is ultra-humble though lol (I don't even have a solar charge controller yet!)

12v DC power systems is a sub-niche in both the RV and ham radio communities. I know of someone locally who has most of his house on 12v lighting and some appliances, to be able to take advantage of solar without the high expense and hassle of a grid-tied system.

Yes. The setup in the article is pretty inefficient.

The really big costs start to pipe up with batteries if you want the system to be functional at night and on rainy days

Inverters aren't cheap, but as your inverter size goes up your battery capacity likely scales even faster to account for times when you don't have much sun for 2-3 days. Hopefully that'll change soon! Lifepo4 batteries are the best we have on the market today, but they're not cheap and still require a lot of hard to find natural resources to produce

> my balcony is facing east. This means it only receives direct sunlight from 16:00 onward during spring and summer.

I’m confused. The sun rises in the east. By late afternoon it would not be directly shining on an east-facing balcony, would it? The most sun would be in the morning on that east side, I would think.

I'm mixing east and west, sorry, I'm going to update my article.

It’s always frustrating to me to see an inverter in these setups. All of your digital devices actually run on DC current! Your computer, monitor, phone charger…

Inverters consume energy just being on, whether current is being drawn or not. And they’re expensive!

Without the inverter, a solar panel+battery setup is super simple and I’m curious to see a movement towards low-voltage circuits in homes.

You can easily power all of the lights in your home with a solar panel connected to a 12v battery. Double in size and you can power your TV and router as well.

This isn’t going to save you a significant amount of money though. It’s just interesting. Big ticket items like your water heater or air conditioner consume a lot more power and will probably need an inverter, etc.

The key issue is that all my existing equipment is 230v. I would have to rebuy everything.

If you need an inverter anyway for hvac, you have added complexity and no gains. Although not mentioned, I’m using 230v ikea fixtures with 12v led e27 bulbs wired to 12 volt, as you mentioned. Is indeed quite efficient, no inverter running.

Yeah, but the annoying thing (from an engineering elegance perspective) is that most of those appliances that are on 230VAC convert to 12-48VDC internally (e.g. TV/monitor, LEDs).

Yeah regarding those appliances 100% I see the inelegant solution.

Imagine all new equipment below x watt would be required to have a 12v input in addition to 120/230

I always thought it would be cool wire parts of your home using PoE (power over ethernet) if you had some solar panels and a battery bank.

Yeah, I think PoE is 48V but it would be cool for adding connectivity to everything. WiFi more or less solves that problem these days though.

I know there are POE lighting panels for commercial spaces. When I looked they were pretty (prohibitively?) expensive. Maybe when powered by solar there are network effects that make them cheaper in overall system cost.

You really don't want to run HVDC through your house. Solar panels in a string configuration make 100's of Volts, and what they produce is changing depending on the load and the amount of incident sunlight. So you would always have some kind of DC/DC conversion going and that's an inverter in all but name.

You really don't want 12V if you DC either, the currents will be ridiculously high and for what you have saved on an inverter you'll be spending it on cabling and fuses. Much, much better to just go with AC and wire it straight into the distribution panel, it will save you thousands compared to a DC system of comparable power and the DC system will never be as safe (because breaking a DC circuit that carries 100A or more is very hard to do in a non-hazardous way using gear available to ordinary mortals).

I’m curious to hear more about the difficulty of breaking DC current.

I was also thinking planning to research more into GFCI for DC current. Seems like it’s possible if you tie the negative terminal to ground just like with AC but that feels weird to me. I guess cars usually have the negative terminal tied to the chasis so it seems reasonable.

Low voltage, high amperage is definitely going to cost a lot in cabling though, that’s for sure.

My understanding is that the only reason AC is preferred to DC for transmission is because it’s easier to transform. But rectifying is super simple and cheap — I wonder what the primary drawbacks are of using DC in homes…

AC goes through zero 50 or 60 times per second so that helps you to interrupt a running current. DC runs steadily, continuously so if you try to break a DC current it will arc like mad and with a bit of luck you'll end up losing your contacts the very first time you try to break the circuit under load. DC in homes is not used because lots of gear relies on the AC frequency to provide a rotating field (easy to achieve with a capacitor).

In some whole-house solar systems, there is a DC component.

I find this interesting:

https://www.generac.com/generaccorporate/media/library/conte... [PDF]

Generac has a whole-house power system with a DC generator as part of the system.

I don't see why there can't be a "DC power panel" for dc-only compoents where it makes sense.

also, there are POE lighting systems (although when I looked they were expensive):

https://www.axislighting.com/innovations/poe-lighting

Yeah totally.

I think the main hurdle is just the fact that a DC circuit isn’t saving any significant money… But as a quality of life improvement, I could totally see this as a selling point for rural homes: 100% off-grid for everything except for heating/cooling. StarLink is pretty power hungry, but still, DC scales up pretty easily.

I remember reading about there being a difference between a typical generator and an inverter generator. Apparently inverter generators are newer and more fuel efficient… so it’s interesting that even generators output DC these days…

I've noticed two things about inverter generators:

noise - they are quieter because they decouple the frequency of the electricity from the generator RPM. "normal" generators turn at a fixed RPM, which becomes the 60hz component of the AC output. inverter generators allow the generator to run at lower speed that is generally much quieter.

power - They seem to be smaller, usually less than about 3kw probably because the cost of the inverter scales with capacity. It's easier to package a 2kw sinewave inverter with an engine to get a modestly price generator. But I haven't seen 7kw inverter generators generally available. But looking for standalone inverters there seems to be a sharp increase in price of inverters of that size.

I'm a little confused about the need for the inverter here.

The SmartSolar can provide output the Pi can use. Why not just throw a 12v-compatible USB power supply on there?

Going up to mains then back down to 5v seems inefficient. Am I missing something?

edit: I'm wrong! My SmartSolar has "LOAD" output but OP's does not. Ref: https://www.victronenergy.com/solar-charge-controllers/smart...

Still, there's the UUGEAR Zero2Go board that you might use to step down from 12v to 5V:

https://www.uugear.com/product/zero2go-omini-wide-input-rang...

IMO, these types of listings (power supply for <insert popular development board>) prey on people who don't have a ton of EE knowledge. A pack of 10 2A buck-converter modules from Aliexpress will run you about $5

Why do you think the Pi is powered via the inverter? I can't see mention of this, and the picture of their setup shows the Pi being powered by a step-down from 12 V.

That picture is not his setup.

I'm talking about the picture with the caption "the latest iteration of my solar setup".

Maybe you tripped over the text "So I decided to build a new setup inspired by Will Prowse solar demo setups, which is pictured below:", which I understand as "So I decided to build a new setup, pictured below, which was inspired by Will Prowse solar demo setups:".

If it isn't, then my question "why the inverter" still applies I suppose. Anything else might just be out of scope or not shown, I'm not sure. It just seems like overkill for just the pi and display.

edit: His desktop computer is powered by this at times. Not pictured and not labelled on the photo. Makes sense though.

The author already powers the Pi directly from the battery, and they switch off the inverter when it's not used. (see the image diagram and one of their responses in the comments) Anyway, you wouldn't need a 'load' port in the charge controller, just put it in parallel with the battery.

I run a similar toy system with a 180w panel and it makes about 110wh a day on an average from march to October - due to a similar bad position the monitoring plug would use more power than the panel makes the rest of the year :P

It runs an inverter and offsets my electricity use.

I plan adding a battery this year but my MPPT charger has been stuck in Hannover for 3 weeks now - I suspect a customs issue.

I see a safety hazard with the exposed battery terminals (as shown in the picture "A 12 Volt 230 Ah lead-acid battery"). AFAIK, lead-acid batteries are less powerful than Li-ion/LFP but would probably still start a fire or give nasty sparks if something metallic falls onto the battery. (I'd be happy to be corrected.)

> The drawback of a 12-volt system is the relatively large currents required to charge the battery and power the inverter. This requires thicker, more expensive cabling to prevent energy losses in the cabling.

Arguably it's only for the discharging via the inverter that you need the thick cables, as otherwise they don't need to be thicker than the cables from the panels. (The current for charging could be much lower than the maximum discharge current.) -- Except if the MPPT steps down the voltage from the panels to the battery by a lot.

See the footnotes.

You don't need an inverter if you're just using an rpi. You can get away with a cheap 12v car USB adapter. I do this for my off-grid wifi (rpi and 5g phone plugged into USB).

If you only serve static files you can use Arduino (or better) MCU (it has lan shield) and decrease power consumption three times, and 18650 instead of car battery can perform better.

Being in the Netherlands makes this very challenging indeed. I am from the Netherlands but don't live there anymore. I came to visit family in December a couple of years ago instead of the usual summer trip and I had forgotten how incredibly gloomy it gets. Short days, dark, low hanging clouds much of the time. Not much solar energy on those days.

Indeed, December here we made all of 85 KWh, whereas the peak day in April so far produced 68 KWh and I fully expect summer days to be much better than that still. So that's a ratio of 1:30 between winter and summer!

The worst day in April so far was 13 KWh, the worst day in December was 0.3 KWh. So no matter what you do, you'll end up using power from the grid. And no realistic battery system is going to give you three months worth of storage. At best you'll have two days worth, maybe three.

east facing window gets light in the morning, not afternoon/evening…

in flat country with no trees and other houses around yes. all it takes is a shadow and you might get more power in the afternoon from the white wall of a house across the street.

I just checked - the panel on my toy system faces directly east but only gets about 2ish hours of non-optimal light a day (between 10ish and 12ish - after that there are chimney shadows) due to houses being in the way. This is peak in summer - for the rest of the year i get less because the sun is lower longer.

That's what I thought throughout the article. I wonder if it is a typo or the author is confused about East and West?

If you search for east on the page, it comes up 4 or 5 times. That doesn’t seem to be a typo. And since the time is written in 24h notation, I also don’t think there is a typo there.

It's funny seeing this mistake crop up once in a while, when in my native language "east"="sunrise" and "west"="sunset" :) You distinguish between them with prepositions ("in sunrise" vs "at sunrise").

I mixed east and west, now fixed in the blog.

I may be out of the loop with prices but 2000€ sounds like a lot for such a small setup. Maybe the tradeoffs of going smaller are worse than I thought, but for ~3500€ I got what I roughly estimate to be worth about 3x as much in generation and storage.

I think that tracks. He seems to have spent several hundred on the panel, frame, wiring to his board and a right-sized battery. You would have incurred those per-watt expenses two more times. Most of the other costs to invert, switch source, and store power are fixed.

He seems on track to build out his system even further, based on the intro, too, so he’ll probably catch up with you.

The frames cost is 25%, which you wouldn’t have. Larger setups are often more efficient in price and performance. Going small is indeed expensive.

I often wonder if wind power could be harnessed in a similar manner on a balcony. Anybody try this to power their blog or saw someone else do something similar? or is this simply unfeasible?

Wind is tricky depending on where you live. In the US there are surprisingly few places where smaller consumer-grade windmills make sense. Its been a while so this may be off, but I want to say you need a consistent wind of something like 10-15mph for most turbines to be of any real use

Even then, a 3000W turbine is usually best on something like a 30-50' tall pole

In certain areas wind can be efficient, in most areas (at least in the US) solar is much easier to deal with and more reliable

Wouldn't a small wind turbine make more sense in the Netherlands?

On a random balcony in a city? I don't know how efficient turbines are, but that doesn't sound very promising.

I think that wind turbines are harder for DIY because they need to be mounted well above the roof height to get non-turbulent airflow.

really small wind turbines are almost never worth it

No, it wouldn't. The capacity factor for a small, unidirectional turbine in non-laminar flow is going to be somewhere between 0 and 15% depending on how lucky you are with the prevailing wind direction. Small turbines also tend to be quite noisy. There was a small unit that was sold by a Canadian solar/wind installer that was named the 'Whisper', but we privately called it the screamer (and it was one of the main reasons we ended up building our own turbine, all of the ones that were on the market were small, loud and inefficient because they were all fixed pitch).

There's also the problems of mounting on a structure, let alone on an apartment building with limited exterior access (as with this case).

Turbines vibrate, and over time can cause joints to weaken as nails are loosened.

That's even without considering the disruption to laminar flow (e.g., full wind efficiency) caused by diverting wind-flow over a structure.

Upshot is that if you do want a wind turbine and have a viable use-case, you'll still want a free-standing tower well clear of structures, trees, etc.

All agreed, definitely never mount a windmill on a structure that wasn't designed with that purpose in mind. You'll definitely live to regret it. Assuming the windmill doesn't kill you...

Ditch the inverter and you are set.

Please read the article or at least look at the image of their setup; they only switch on the inverter occasionally to power their main computer and monitors

Can someone recommend a brand of solar panels or a retailer, preferably in europe?

It does not really matter, they are basically all the same. Only thing to watch out is that they should be build with half-cell technology and monocrystalline (which almost all of them are, technology does not differ that much in solar panels). 400 W Panels are pretty much standard.

I think most countries in Europe would have local solar panel sellers. I'm in Ireland which is usually pretty bad for availability of things, (for example, there's no amazon.ie - we have to buy from UK or DE) and even here we have solartricity.ie, solarstore.ie and several others.

Longi panels are what I got, if you want a recognisable brand name Panasonic also do them.

So; how much did the whole setup cost ?

It says 2000 EUR at the bottom.

Magnets can generate energy.

>Suddenly you realise that making the background on all monitors black saves ~20 Watt.

Depends on panel type - some are lower @ white

Curious, do you have any examples of monitors like that? Less light and lower brightness reducing power consumption is intuitive, the inverse less so.

Some LCD screens. It's pretty marginal though

https://www.quora.com/Does-a-white-background-use-more-energ...

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