alt Hacker News> spend hundreds of hours building a home battery system
That is, in my opinion, the worst feature of this entire project. It is cool and nice and fun. But it takes a lot of time to research, acquire skills, get tools and build.
> you could just buy for $20k
I agree with a broader point but that particular price is extremely high and far from reality.
A reasonably good 18650 cell has a capacity of ~12 Wh (~3300 mAh * ~3.7 V = ~12.2 Wh). The battery mentioned in the article consists of "more than 1000" such cells. Let us assume 1200 cells. That would mean it has a capacity of ~14.4 kWh (1200 * 12).
It is possible to get a pre-assembled steel battery case on heavy-duty wheels for 16 LiFePo cells, with a modern BMS with Bluetooth and wired communication options, a touchscreen display, a circuit breaker and nice terminals for ~ $500. And it is also possible to get 16 high quality LiFePo cells with a capacity of ~300 Ah each, like EVE MB31, for significantly less than $100 each. This means that for less than ~$2000, it is possible to get all components required to assemble a fully working ~15 kWh LiFePo battery.
- That assembly would take a few hours rather than weeks.
- It will have new cells rather than used ones.
- It will be safer to use than a battery with Li-Ion cells.
- It will likely take much less space.
- It will be easy to expand.
Replies
Thanks for the all the specifics! I admit that my $20k number was a very rough "I'm sure it must be less than this" estimate because I wanted to make sure I erred on the high side for the point I was making.
The parable of the fisherman and the banker:
https://travis.vc/mexican-fisherman-parable/
Sometimes the doing is the fun part.
> - It will have new cells rather than used ones.
This is not a feature. Our Earth is a limited resource, and being able to reuse batteries instead of discarding them to the trash is a desirable property.
300 Ah * 3.2 V => 960 Wh ~= 1 kWh
$80 per cell (before shipping) on the top Google product result for EVE MB31.
That's a good bit cheaper even than when I looked last, in early 2021.
And there's a non-zero possibility he burns his house down and doesn't have anyone to sue over it.
At least if he bought a commercial battery and it experiences a lithium fire, he might expect to file a claim against the manufacturer, or his insurance company might on his behalf.
You can get 15 kWh for $1,3000 if you pick up in Texas (these use EVE MB31 which usually end up testing at ~310 Ah): https://www.apexiummall.com/index.php?route=product/product&...
It just keeps getting cheaper and cheaper every year...
Now.
I will point out that in 2016 when they started this project, the cost of new batteries would have been multiple times higher than it is today, so it would have been a moderately more "sensible" thing to do than it currently seems.