Comment by ianferrel

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.

Now what?

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

What 13000? Here in the EU we pay around 3-3.5K for 15 kWh.

$1,300.00

typo sorry, $1,300.00

13k or 1.3k?

There is a spectrum of DIY and the sweet spot depends on the person. Since I'm good with electronics my sweet spot is buying premade packs.

I think Target isn't the right comparison here - the skills required for this project are worth much more than minimum wage bagging groceries. If you assume something like $50 an hour (on the low end for a skilled electrician), you get to the $6800 number in the parent post pretty quickly.

Of the three options, DIY battery packs, premade 100aH battery packs, or white glove powerwall a minimum wage earner would likely not have the skills to DIY the battery packs nor the money to pay for the powerwall.

Battery packs are an efficient market commodity and that’s pretty hard to beat for value for money.

Once full installations become more of a commodity then DIY with premade packs becomes less worth it.

It all comes down to what makes you happy.

There's a lot that goes into manufacturing battery packs beyond the cells. How's your thermal path to ambient in your home wall battery? How is the inter-cell thermal isolation? Is there a path for gas discharge in the event of a cell failure? Is the pack appropriately fused at the cell or module level? When a cell fails, does it take the whole pack with it, catch someone's apartment building on fire and kill a family of 5, or merely become stinky with a hotspot visible on IR?

How good is your cell acceptance testing? Do you do X-ray inspection for defects, do ESR vs cycle and potentially destructive testing on a sample of each lot? When a module fails health checks in the field, will you know which customers to proactively contact, and which vendor to reassess?

Yeah lots of batteries are 18650/26650 in a trenchcoat. The trenchcoats run the gamut from "good, fine" to "you will die of smoke inhalation and have a closed casket" in quality and I think that bears mentioning.

Probably, but EV batteries are large enough that there might be an industrial recycling process for them, while old laptop batteries are basically free because it's too much labor to extract useful value from them.

> You would be amazed how many battery packs are multiple 18650s in a trenchcoat

Also laptop batteries used to be many (usually three or six) 18650s in a plastic trenchcoat.

You could literally rebuild your battery when it died, and pick the cells you liked the most. In theory you could pick higher-quality cells than those you find in the batteries sold on ebay from chinese stores. In theory.

>You would be amazed how many battery packs are multiple 18650s in a trenchcoat

$50 of 18650s in a $500 trenchcoat with DRM protection. So wasteful.

That depends on the problem you're trying to solve. If it's only to build a home power system, sure, but if the goal is "I want to prevent these laptop batteries from ending up in a landfill" then using an old EV battery doesn't really help you much.

FWIW a lot of EVs use prismatic cells, not cylinder cells. Tesla, Rivian, and Lucid use cylindrical cells. Hyundai, Volkswagen, BMW, GM, Ford, and BYD all use prismatic cells.

I feel like for home battery backup there needs to be some kind of lower energy density solution that has zero fire risk.

Weight is not a factor for home energy storage, there is no need for lithium cells.

This can't be done remote so you will need to bring that labor to where the work is.

The dude has a warehouse/workshop to do this work and house the system. I’m super impressed by what he’s accomplished, don’t get me wrong; but, what he’s done just isn’t viable for 99.99999999999% of people.

Give me an array and battery system that can pull off the grid and/or array and power most of my home without me having to think a whole lot or pay a vendor thousands to install while making the total cost under $1000 and I’ll do it.

Until then, it just isn’t financially viable when my electricity costs are well under $70/month average across the year.

Recouping the costs for install of solar systems are estimated at 30-40 years as of 4 years ago when I researched it. I’m sorry, but that’s just not worth it for me and most others.

That is why you sort them.

Some recent research into that: https://www.sae.org/publications/technical-papers/content/20...

You can also consider maintaining packs together to avoid complicated disassembling processes.