Toyota is recycling old EV batteries to help power Mazda's production line

Those who TL;DRd - it's for the factory, not the cars!

Old EV batteries are great for energy storage. A worse weight-to-capacity ratio doesn't matter for batteries sitting on the ground. A battery that holds only 70% of its original capacity is considered worn-out for EVs (and even replaced under warranty), but grid storage isn't driving anywhere, so any capacity left is still useful.

If you take car EV batteries and use them for stationary storage when past end-of-life, the fire risk becomes fairly substantial because EV batteries often have a little water ingress, physical damage etc.

It can be solved by isolating each battery in its own steel box, but that gets fairly expensive fairly fast.

How much distance does one pack realistically need to not cascade? Honestly I can't imagine any more than half a meter since air is an extremely good insulator. Just make sure the fire can't crawl across though cable insulation?

I've personally set RC lipo on fire with the wood-nail-hammer technique and while the fire out of the pack is intense I can't imagine it igniting another pack.

Precautionary principle. There’s not good ways to extinguish these fires once they start. So you kinda have to let them go. Maybe you could use some sort of deluge system or aggressive liquid cooling on the surrounding cells however. Overbuilding the delivery system but then running the pumps at their most efficient cfm except when the smoke alarms go off.

Do we use the precautionary principle when we run nuclear, build dams and burn coal as well or is this an extra thing because it's a potentially good way to reuse EV batteries? I don't think we should build these hand-me-down EV batteries near population centers, but my understanding is that the worst case scenario would be the plant burning down and releasing bad things (hello coal & natgas) into the atmosphere?

If we could develop some basic standards for packs (which voltage steps per row and some kind of connector interface standard like for charging) I think we have a really good way to maximize the lifetime and use of EV batteries to help the environment.

I paraphrase Bill Gates: There's no one energy source which will save us, many will complement eachother.