> 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.
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.
Yes, of course, this cost consideration is only relevant today.
I can imagine that ~9 years ago there might have been very little reasonably priced LiFePO4 cells available and if someone could get their hands on used 18650 cells very cheaply, it might have been a reasonable choice at the time.
Particularly if you can narrow down a couple brands where it tends to be a single cell or two that goes poopy while the rest are still good. Driving around picking up dead batteries that only have 1-2 good cells per pack is a thankless job.
Now what?
The costs their parent mentioned are the costs now, not back when the system was originally built.
It's likely just a statement of emphasis, though the correct usage would be something like, "now, something something something..." with a comma instead of a period
"Now" as in "all of those things are true now, but they weren't when this project started ten years ago."
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.
There's even more to the riddle. Lithium recycling, cost of the power loss in old cells. Power transmit cost. Cost of power generation on site.
Pick used EV or industrial batteries. This must be much more efficient due to a larger cell size than in laptops.
OTOH used laptop batteries can likely be obtained for effectively zero monetary cost, while used EV or solar backup batteries still cost quite noticeable money per kWh. With laptop batteries, you pay with your time; if you for some reason have an excess supply thereof, or you just enjoy this kind of work as a pastime.
> Our Earth is a limited resource
Of course. No one disputes that. I was just trying to point out that you can get better cells for less money.
> being able to reuse batteries instead of discarding them to the trash is a desirable property
I fully agree. No one is trying to suggest that we should discard used batteries into trash.
We have LOTS of lithium
Maybe we'll run out of ion?
Sort of. Compact NMC Li-ion cells from laptops and phones often use stuff like cobalt, supplies of which are much more limited and problematic than of lithium. The newer LiFePO4 chemistry does not use it, and, importantly, is rather hard to ignite. Its energy density per unit mass is lower, but it's not that important for stationary installations.
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...
What 13000? Here in the EU we pay around 3-3.5K for 15 kWh.
I am also in the EU and last year I have purchased a YIXIANG DIY battery case and 16 EVE MB31 cells for a combined cost of less than 2000 EUR without VAT.
It was shipped from China so I had to wait ~2 months to get it which is a disadvantage. Local warehouse stock was slightly more expensive.