[jstsch]

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... :)

[Dylan1312]

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.

[f1shy]

> 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.

[pjc50]

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/

[testing22321]

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.

[MisterTea]

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

[scarecrowbob]

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.

[ViewTrick1002]

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...

[j2kun]

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.

[jstsch]

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! :)

[MisterTea]

> 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.

[microdrum]

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.

[Barbing]

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]

[tomashubelbauer]

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.