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Comment by CrzyLngPwd | Hacker News Reader

We're off grid and have 7kw of panels, and 40kwh of 48v lithium batteries, with a generator for backup, which is rarely used since we are frugal with electricity and switch everything off when not in use.

I set it all up myself, and while it is not trivial, it's not difficult either.

Learning to put connectors on properly, size cables and put lugs on properly, learn about earthing and breakers...just one bit at a time.

I'm about to set up another system on the roof of an outbuilding to supply power for a water pump and irrigation where we grow food. This will be much easier and simpler since it will have only one 48V lithium battery, but I'll still use Victron stuff and connect it to a Cerbo so it can be monitored.

If I sold this place and bought somewhere on the grid, the first thing I'd do is cut the cord and set up my own system again.

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What inverter hardware did you use?

I have an el cheapo 120 VAC 3600W import inverter with just two 100AH AGM batteries in series as it's a 24 VDC unit. Right now its all temporary and more experiment than practical.

Inverter mounted to a portable frame I built from bolted slotted angle with two battery shelves for a total of 4 batteries (only 2 now.) The batteries have a 200A terminal fuse and run through a 200A disconnect to the inverter using #2 AWG cable. The inverter, AC input, AC output are all grounded to a single ground bar that is bonded to the metal frame. AC Input is fed from a 12 AWG cord with 15A plug. AC output runs two 15A MCCB's, each terminated to a single socket hanging off a short whip cord. A cheap two wire digital DC volt meter is wired in series with a push button so I can see the battery voltage at a glance when I have the inverter powered down.

I temporarily setup the panels in my yard as an experiment but since I am in the city, I don't get good sun in my yard with all the obstructions. Honestly I ran it for two days, took the panels down before it rained, and didn't get a chance to measure anything. The panels really need to go on the roof and I have no intention of doing that any time soon.

The system did come in handy as a backup for my boiler when a wind storm knocked the power out for an hour and a half this past winter. I have thought about setting it up as a UPS for my little IT setup at home but 3600W is super overkill.

Victron MultiPlus-II 48/10000/140-100/100

All of my system, aside from batteries, is Victron and installed in a small lean-to. Batteries are 8 x Fogstar 48V 100AH, in an outdoor rack, since I have no dry space indoors for batteries.

Aren't lithium batteries cheaper than AGM these days? On top of lasting much longer and allowing full deep discharge.

While I realize LiFe batteries are quite safe, at the time I bought this setup I felt more familiar with AGM so I went that route. The prices were also comparable and I can use these in a truck project I also have.

do you have a blog or some links of walking through the process of getting everything setup?

I don't, but Will Prowse on YT is very good, and lots of other people are too. Victron has great documentation, and lots of system layouts as examples.

The most challenging part was getting and victon stuff talking to the fogstar batteries, which was hampered by not reading the manuals and trusting chatgpt, but in the end it was trivial.

Curious, how did you deal with inspections and building codes? Or is it in a county with no building codes?

If it's not grid connected, you can get a way with a lot of stuff in many places. But if you live in the middle of nowhere, you can just buy a lot of stuff on amazon and wire it together in plug and play style.

I was watching a Finnish guy over the weekend on Youtube (handle True North) that recently took his self built solar powered boat from Helsinki to the Mediterranean, via about 3000km of water ways through Germany, Switzerland, France, etc. In the winter! He just got there a few weeks ago. This stuff is easy if you are a bit handy. He used cheap ply wood and epoxy to glue the thing together. I think he has maybe 4KW worth of panels on the roof, a 6KW motor, and about 16kwh of battery if I remember correctly. Mostly he runs the boat at ~3.5KW because the boat's shape actually limits the speed. More power doesn't make it go much faster. The impressive thing here is that this boat is super simple and it works. He charges using solar panels. On a sunny day he arrives with a full battery. On a cloudy dark winter day, he can still do tens of nautical miles. And he only needs a few hours of daylight to charge up his batteries.

I have a similar situation with a smaller system in rural CO (4kw panels, 6kw inverter, 15kwH batteries).

If you get far enough out it ceases to matter.

The (unpermitted, about 25-year-old) shacks I live in never had power and getting an easement was prohibitively expensive. It doesn't impact anyone but me (and potentially my son, who will inherit this mess when I die in 30 or so years).

There are codes here, and codes enforcement. But it's largely complaint driven and I suspect that all my neighbors are in a similar situation.

If I were in town and could get utilities I'd prefer that, but the county won't even pick up the last 1/2 mile of roads to where I am living... maybe if they'd do that I'd consider only building things that are permitted.

I live in the UK, and I didn't invite any inspectors for a review :-)

You also run the risk of insurance declining your claim due to unauthorized or self-installed electrical work, even if your work wasn't the source of a fire/problem.

At least in the US, you're not going to see any building inspectors out in the country unless you're trying to sell the property.

Man, I need to learn from you! My wife and I are building an offgrid cabin right now and I was just trying to figure out some of the specifics!

Very cool!

I think we’re actually going to use lead-acid marine batteries? But very similar plan. We’re going to need a LOT more solar though than you I think. The winter here in South Central Alaska is pretty bleak in terms of available power. Still, very cool to see someone else living the dream!

Go straight to 48V lithium, you won't regret it.

I have thought about this, but getting them shipped here is hard (not impossible just a pain) and I don’t think I can service a lithium battery? I can service a lead acid battery and they’re ubiquitous in the marine industry around here, but I’m also not an EE.

Got any reason why I should go for the lithium over lead acid other than the size?

Thanks!

You can switch cells if you need, or switch the BMS if you need, heck, you can build a lithium battery from cells and wire your own BMS.

With lithium, you hvae a deeper depth of discharge than lead acid, but you're better off reading about the pros and cons and making your own decision.

My system started with 3 x 12v100ah lithium batteries in my van, with panels on the roof, and a dc-dc charger for backup, which worked amazingly well, but for faster charging with larger panel arrays, 48v is the way.

With my 12v I could charge 1.2kw per hour maximum, but 48v means I can charge 4.8kw per hour, which means in winter, with at most 4 hours of good sun on my panels (due to trees), I can put in more than I consumed.

> If I sold this place and bought somewhere on the grid, the first thing I'd do is cut the cord and set up my own system again.

Why?

Reliability, no changes in charges, and self-reliance, to name a few.

»We're off grid and have 7kw of panels, and 40kwh of 48v lithium batteries, with a generator for backup, which is rarely used since we are frugal with electricity and switch everything off when not in use.«

Good for you, but this is neither a concept for large cities nor for the industry.

Good for you but we don't all live in large cities or participate in "the" industry.

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