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Comment by jstsch | Hacker News Reader

Battery prices are getting really low, if you're willing to do some DIY. Just received a 15kWh battery from China. A 'Humsienk'. Combined it with a GroWatt SPA3000TL-BL inverter.

Total price, 1600 euros. So close to the magical 100 euros per kWh. Driving it with some interesting combinations of Raspberry PI's and serial interfaces and custom written Go code, but it works... :)

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Did the same, got a solar installer to fit panels on garage and a solis hybrid inverter. They fitted a CT clamp on my meter and a lora device on both sides for it to communicate with the inverter.

Then bought a 16kwh battery for ~£1500, installation was plugging in a positive, negative and ethernet cable and configuring the inverter to use the battery. (if my home insnurer is reading this, I had an electrician friend double check while helping with some other work)

Definitely recommended for anyone who likes tinkering, thousands cheaper than installer pricing.

> Battery prices are getting really low, if you're willing to do some DIY.

Willing and allowed. In some countries it can only be done by certified electricians.

UK considerations: must be at least signed off by an approved electrician ("Part P" regulations), and for any situations involving subsidy needs to be MCS approved as well. https://mcscertified.com/

Surely it only needs to be signed off if you intend to sell the property with them or sell excess back to the grid. If youre just using the batteries how is anyone going to know?

shrug if you can rely on nobody noticing, or non-enforcement, sure, but it is actually a criminal offence not just an administrative requirement.

If is something does happen, and Li Batteries catching fire is not something unheard of, you will be in a world of suffering. Probably having no home, and having to pay damages to the neighbors. All to save what? 2k$... 5k$?

I'd assume your fire insurance covers nothing if illegally installed batteries are found inside after a house fire.

If your house burns down for any reason, not necessarily the DYI batteries, the insurance company will know anyway.

If the DIY work wasn't the cause for the fire it shouldn't matter, but I half-expect someone to inform me that US insurance companies can (legally) deny coverage for reasons unrelated to the accident.

How are you going to absolutely price that the batteries didn't start the fire or even just make the fire worse?

You can't and you will lose in court.

I wouldn't have to, where I'm from the burden of proof is on the insurance company.

Not so fast. Have you very carefully read the full small print of the insurance policy? Did you review that with a lawyer? Is incredible how different "normal" people vs. lawyers can understand a contract.

I'm pretty sure there is a clause, which states that you have to inform if you have and/or are not allowed to have fire loads, or anything that could cause a fire, or make it worse, or something along the lines in legalese. These formulations are always there because of people hoarding fuel in the basement, for example, or O2 Tank, or whatever. They are formulated in the most generic way possible to catch anything you do "wrong". Failing to follow such clauses, also when not explicitly stated, is dropping your obligations in the contract. And then there will be a clause that of course says, that not following the contract from your side, also exempts the company of paying.

Note also there are clauses that are very softly specified, like "use rooms for the intended purpose" which may be a problem if you store idk, paint in the garage, which may be flammable, in which case a fire in the garage will not be (at least fully) covered.

Ask me how I know...

Find an electrician who will inspect and sign off on your work. It's not illegal as licensed master electricians have mechanics do all the grunt work who are unlicensed. The electrician vouches for his employees work which legitimizes it. No different than you doing the work and having the electrician inspect, call out issues to fix, and inspect again until no issues are found and sign off.

I mean, it "can" be done without a certificate.

It "may" not be permitted, but if you live in a collection of shacks in rural Colorado that were themselves -already- completely un-permitted then you might decide that it's best to just do the work yourself.

Then pay one to inspect it and sign off for you.

Theoretically a good choice, but where I live, just doesn't work. Either they just say "no thanks" or they will be more expensive than letting them do the whole job.

I got the "trick" recommended to do the things yourself, then call a certified guy, and say "look, I contracted a guy, I had no idea, he came did everything, but I got a bad vibe, I would like you check the whole installation". But it also does not really work, they will come with a contract, where you are enforced to contract them to correct any findings. And boy they will find things then...

It varies for sure but in my case it helps to know people.

I paid an electrician one hours work to actually connect my inverter to my main 200A panel, and he even got the required building permit required.

We are finally starting to see Chinese prices externally.

It’s been crazy seeing the western home storage market selling systems with the €/kWh being more expensive than buying a BEV. And that includes a car.

https://www.docanpower.com/eu-stock/zz-48kwh-50kwh-51-2v-942...

I do wish I could have a good, in-depth tutorial on how to set this up myself. Along with (pipe dream) an explanation of how it would interact with my local utility. I worry that due to some silly technicality, I won't be able to export to my local utility, or else I won't be able to run off-grid when there's an outage.

I will do a write-up in a couple of days. It's all relatively simple, you just have to expect terrible documentation and do a bit of reverse engineering and serial sniffing. I expected the battery to be complicated, but it turned out that the inverter was.

You'll encounter stuff like: manual says use RS485 port on Battery for GroWatt inverter → need to use CAN port on Battery. Meter Port (RS485 [serial] over RJ45) wiring on GroWatt is unknown (A: white orange / B: white blue, cross them over). Dinky RS485 serial → USB converter needs a 120ohm resistor between pins for line termination. Growatt meter port expects a SDM630 meter, not a DTSU666 (hardcoded), so vibe code another emulator. DIP switches for RS232 connection need to be both on the ON position (undocumented). CH340 USB→serial converter for RS232 does not work, but one with a Prolific chip does. Etc. etc. etc :)

Oh, and the biggest one... I was expecting to be able to just send a command, 'charge at 500watts', now... 'discharge at 2000watts'. But no. You have to emulate a power meter and the inverter will try to bring the net power to 0. Fun! :)

I would appreciate this write up as well. Looking to do a DIY setup.

> Driving it with some interesting combinations of Raspberry PI's and serial interfaces and custom written Go code, but it works... :)

What protocol is it speaking? I've seen some of the more mainstream models call out that they use Modbus but all the cheap import models either might use Modbus or some custom protocol you have to reverse engineer or hope someone else did.

Yup, Growatt is the Chinese OEM that Base Power white labels to pretend it does US manufacturing. In fact this stuff is low quality. You need to be careful. There are gradations of quality at cell, pack, inverter, control levels. You will be crushed if you realize you AliExpressed your way to a home power "solution" only to have it fail young.

Awesome.

Feel you have more unknowns on the safety front? vs. the expensive off-the-shelf. [in the USA, it’d also be “fewer names to sue” in that unlikely tragedy of combustion in home, but no euro/kWh targets there]

LFP batteries are as likely to burn down your house as a stack of wood is. I'd be worried about the inverter or botched DIY wiring (especially not to spec torque on terminal connections and botched crimps leading to hot spots), but not about the batteries themselves. For a person who wants to save some money, but doesn't know how to work with electricity, the best move is probably to get cheap LFP cells from China, but have a professional install a BMS and the remainder of the solar system.

> especially not to spec torque on terminal connections and botched crimps leading to hot spots

This was indeed my greatest concern. However the battery came with pre-crimped very solid DC wires, and nice push connectors for the battery itself. The battery also has an integrated DC breaker (great!).

The system runs 3KW max, so I just added an additional breaker (with RCD integrated) in the conduit box. In NL this is something a DIY-home owner easily can do themselves :) (just use the right solid/flex stranded cabling for the connectors, etc...)

And further, my position has been that learning the correct methods, paying a lot of attention to details, and not being cheap with tools is -still- cheaper and probably more reliable than paying contractors. I have only used my hydraulic crimper for a pair of cables, but it was the correct tool and did good work.

I'm not interfacing with a grid, and there are already code issues with my places- I'd probably feel different if I could get insurance on my place.

Cheap chinese tooling and youtube (plus pretty good general literacy) go a long way in this world.

And FWIW, I live in the US west and am way more worried about fire coming from outside than from the batteries.

> botched crimps

On a tangent, I’m amazed at how bad most random crimps I see on the internet are. Also, the number of people who debate the use of solder on crimps without discussing potential issues with said solder is too high.

> LFP batteries are as likely to burn down your house as a stack of wood is.

LFP batteries are much safer than past chemistries, but this statement is way too broad.

High power batteries are always more dangerous than something like a stack of wood, because batteries will gladly dump their entire energy capacity very rapidly into a short.

Even if the battery itself [mostly] won't self-immolate, the entire installation can be a fire hazard.

Treat them with proper respect.

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