Glubux's Powerwall (2016)

>the solution came with rearranging and adjusting the cells to ensure the packs worked more efficiently.

>Glubux even began disassembling entire laptop batteries, removing individual cells and organizing them into custom racks. This task, which likely required a great deal of manual labor and technical knowledge, was key to making the system work effectively and sustainably.

This kind of thing is cool as a passion project, but it really just highlights how efficient the modern supply chain is. If you have the skills of a professional electrician, you too can spend hundreds of hours building a home battery system you could just buy for $20k, but is less reliable.

There HAS to be a way to automate this process and make it work at scale.

You would be amazed how many battery packs are multiple 18650s in a trenchcoat. Even EV battery packs use them. Though it does raise the question - wouldn't an old EV battery be a better solution than stripping apart laptops?

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.

I get that the trenchcoat needs to be well designed and tested, but I am still flat out amazed that you both agree with “meh, most battery packs are made up of rechargeable domestic batteries you find in a kids toy”

I just assumed there was … special stuff in there

For a highly engineered battery like a premium EV, there are coolant channels, temp monitoring, voltage monitoring, etc.

Soldering some connectors onto some random cells and knowing they shouldn't go over 4.2v is one thing, but measuring cell health via internal resistance, programming a controller to do temp shutoff and wiring up temp sensors, keeping cells balanced, is a lot of extra work, but critical if you at all care about not potentially burning down wherever they're stored.

Keeping the cells small and just using a hundred of them in parallel (and a hundred of these parallel packs in series to get up to the hundreds of volts needed), thus using ~10,000 cells, in EV batteries limits the maximum damage from one cell going worst-case, assuming your enclosure can contain it.

That being said, it seems there is a slow movement towards larger cells, from 18650 to 26650 or similar. But each cell on its own is still a dumb can of chemicals ready to go boom if you mistreat it.