Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

thedrive.com

Post reply on HN
Print view View original

41–50 of 142 posts

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

#41

Post by londons_explore »

pornel wrote: post #28

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.

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

#42

Post by bluSCALE4 »

whatever1 wrote: post #29
pornel wrote: post #28

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.

At the cell level they don’t degrade linearly. First it’s slow then it’s fast and then it’s abrupt collapse. You probably have noticed that yourself with old devices. Some do not hold charge even for a minute. With battery packs probably you can do some smart things to make the degradation curve look more linear, but again there is only so much you can do.

You do realize these batteries you're referring to resale at a decent price because, for the most part, they still function really well, just not in its existing capacity.

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

#43

Post by lillecarl »

jama211 wrote: post #36
whatever1 wrote: post #29

Earlier quoted context omitted.

At the cell level they don’t degrade linearly. First it’s slow then it’s fast and then it’s abrupt collapse. You probably have noticed that yourself with old devices. Some do not hold charge even for a minute. With battery packs probably you can do some smart things to make the degradation curve look more linear, but again there is only so much you can do.

There’s quite a lot you can do when you can isolate and deactivate individual cells, big battery packs like this really do not fall off a cliff in the same way you’re describing.

How do you achieve this with cells in series? Do you kill an entire row and put it on "maintenance voltage"? I know how balance charging RC batteries work but they're smaller scale and "single row".

Also in RC car world it's generally preferred to have one cell per voltage step, I've had way more dual-cell(per series) packs fail than single ones. Though my experience is only 6s/~22v but it's "the same shit on a bigger scale" as far as I can comprehend.

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

#44

Post by neogodless »

redwall_hp wrote: post #16
bluGill wrote: post #2

had to check: toyota owns 5% of mazda which makes them the largest shareholder.

Toyota also owns Daihatsu, which is a lesser known name in the US, but is a major maker of kei cars, which are huge in Japan and other parts of Asia. They also own Denso, which is the second largest auto parts company. And they partner with Subaru on some things, such as the Subaru BRZ and Toyota GR86, which are basically the same car with different badging.

re: Subaru

Perhaps more relevant, the Subaru Solterra and Toyota bZ4X (renamed bZ for 2026) are on a shared EV platform.

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

#45

Post by byw »

londons_explore wrote: post #41
pornel wrote: post #28

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.

Maybe they can also make the boxes out of concrete for a lot cheaper?

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

#46

Post by lillecarl »

londons_explore wrote: post #41
pornel wrote: post #28

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.

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

#47

Post by hinkley »

pornel wrote: post #28

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.

Battery banks are worse than degraded raid arrays in some important respects. The bad cells tend to try to bring the rest of the pack with them. It’s one of the reasons people keep toying with partitioning cells and putting controllers onto individual cells or small groups of them.

Parting out two or three dead battery packs to cull the best of the survivors can improve things quite a bit. And as you say, on a stationary pack you can afford to overdo telemetry, cooling, and safety circuitry because it doesn’t have to move, let alone accelerate.

I don’t know what the half life is like for the reused cells though. Do the cells that lasted twice as long as their neighbors continue to outperform or do they revert to the mean over time? I could see either being true. The days when you accidentally produce cells that are several stddev better than your target quality should make cells that last longer, unless they’re sold to a leadfootted driver.

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

#48

Post by londons_explore »

lillecarl wrote: post #43
jama211 wrote: post #36

Earlier quoted context omitted.

There’s quite a lot you can do when you can isolate and deactivate individual cells, big battery packs like this really do not fall off a cliff in the same way you’re describing.

How do you achieve this with cells in series? Do you kill an entire row and put it on "maintenance voltage"? I know how balance charging RC batteries work but they're smaller scale and "single row". Also in RC car world it's generally preferred to have one cell per voltage step, I've had way more dual-cell(per series) packs fail than single ones. Though my experience is only 6s/~22v but it's "the same shit on a bigge…

No EV that I'm aware of has the ability to bypass a single cell in a series string.

I have often wondered if it would be worth designing an EV battery that can permanently short out a bad cell in a string, perhaps by deliberately disabling balancing, letting the bad cells voltage fall to zero, and then perhaps having a single use 'bypass' that latches on.

It wouldn't be a seamless user experience, because if you discharge the cell to say 0.5 volts but then the user tries to charge their car, you can't let them, since you cannot safely charge a lithium cell which has fallen below the minimum voltage, but you also cannot bypass it till the voltage falls to zero. Could be done automatically at 3am though like system updates.

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

#49

Post by hinkley »

lillecarl wrote: post #46
londons_explore wrote: post #41

Earlier quoted context omitted.

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.

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

#50

Post by hinkley »

slt2021 wrote: post #37
pornel wrote: post #28

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.

this is like picking up unfinished cigarette butts and making few finals puffs before burning your mouth. worn-out batteries can swell and fail spectacularly, with fireworks

Car power packs are batteries in the other sense of the word. They can be disassembled and culled. So what matters is the health of the best 1/kth cells in the array not the overall array health.
Post reply on HN