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

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

#71

Post by themafia »

spockz wrote: post #51
londons_explore wrote: post #48

Earlier quoted context omitted.

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 disc…

I guess you can put a relais/switch in for each cell in a series but then you need to account for voltage differences when taking them out. Either by over provisioning within the series and rotating in different cells. Or by have other strings take up the slack. Either way you need some form of overbooking / compensating capacity.

A relay would allow you to switch it out and then back in again. Which you don't need. Just a fusible link that can be blown to permanently disconnect the battery from the string might be simpler and more ideal for the application.

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

#72

Post by lazide »

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.

Eh, the math is probably pretty different with massive quantities of packs in racks.

I’m imaging every firefighter I’ve ever known suddenly having the hair stand up on the back of their necks.

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

#73

Post by hinkley »

stetrain wrote: post #65
hinkley wrote: post #55

Earlier quoted context omitted.

You shouldn’t need to charge them all at the same rate. Put in some cells that charge slower, fast charge the rest and continue charging the slower cells until unplugged. Consider for instance fast charging the array to 70% instead of 80%, where 1/3 of the cells are charged to 50% and the rest to 80%.

When all of your cells are connected in a pack of 400-800V connected to a DC fast charger, how do you stop charging the fast cells and continue charging the slower cells?

Separate power factor circuits for each pack, I would think. With everything switching over to GaN now and bringing the prices down that should be doable.

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

#74

Post by axus »

kenhwang wrote: post #53
omega3 wrote: post #39

Earlier quoted context omitted.

> Due to typical Japanese corporation by-laws, it only takes 33% share ownership for uncontested control of a corporation It doesn’t make any sense.

Think of it like how Zuckerberg only owns 13% of Facebook but has >60% of the voting power. Japanese law allows corporations to only require 1/3 of voting shares present for quorum, and then a majority of those present to pass resolutions. It also allows cross-shareholders (like Toyota) to have special privileges over regular class shareholders (typically right of first refusal over any resolution). In practice, noth…

How would they prevent two owners from owning 35% each? Could owner A vote something on Tuesday, and owner B vote something different on Wednesday?

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

#75

Post by arghwhat »

hinkley wrote: post #47
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 statio…

A degraded battery bank does not mean a bank with outright "bad" cells. The cells will probably be way more off than they used to be, but there can still be plenty of effective capacity in the bank. Heck, if space isn't an issue, it's productive as long as it isn't self-discharging too fast.

You can still have a working battery even with some "bad" (i.e., way out of spec) cells, depending on the BMS. All the thresholds are configurable, just that a regular EV setup would lean towards safety.

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

#76

Post by kenhwang »

axus wrote: post #74
kenhwang wrote: post #53

Earlier quoted context omitted.

Think of it like how Zuckerberg only owns 13% of Facebook but has >60% of the voting power. Japanese law allows corporations to only require 1/3 of voting shares present for quorum, and then a majority of those present to pass resolutions. It also allows cross-shareholders (like Toyota) to have special privileges over regular class shareholders (typically right of first refusal over any resolution). In practice, noth…

How would they prevent two owners from owning 35% each? Could owner A vote something on Tuesday, and owner B vote something different on Wednesday?

In theory, yes, if those shareholders each keep not attending the meeting called by the other shareholder, they could both independently pass or undo each other's actions.

In practice in a hostile situation, they'll be courting the remaining shareholders to gain majority and won't miss those meetings, which tend to also have rules about how quickly or often they can be called.

It is also legal and typical for the bylaws to include poison pill provisions that would automatically protect the existing >33% shareholder, preventing a second >33% shareholder from existing (thus requiring multiple smaller existing shareholders to join forces to overthrow the largest shareholder).

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

#77

Post by blkhawk »

arghwhat wrote: post #75
hinkley wrote: post #47

Earlier quoted context omitted.

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 statio…

A degraded battery bank does not mean a bank with outright "bad" cells. The cells will probably be way more off than they used to be, but there can still be plenty of effective capacity in the bank. Heck, if space isn't an issue, it's productive as long as it isn't self-discharging too fast. You can still have a working battery even with some "bad" (i.e., way out of spec) cells, depending on the BMS. All the threshol…

plus if you aren't making your packs unrepairable on purpose with foamed construction (like Tesla). you can par out modules in the packs into new configurations somewhat easily for the amount of work needed.

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

#78

Post by arghwhat »

reactordev wrote: post #63
Dylan16807 wrote: post #60

Earlier quoted context omitted.

Your own cells ? Like you put together a lasagna of metal sheets and chemical goops and roll it up?

Nah, you can buy 18650 cells, nickel strips, a spot welder, and make a BMS. Build your own battery pack.

If you don't know what you're doing, don't do this. Even if you know, probably don't. It works, and is a regular industrial process, sure, but you're trying to perform controlled melting of the protective housing of one of the many, tightly packed chemical energy bombs you're sticking together. Doesn't take too much of a mistake to go very wrong.

If you're building a battery pack in this day and age, use something like LiFePo prismatic cells and bolt-on busbars instead - way less dangerous chemistry, way less spicy process - but realistically speaking just buy the premade packs. For normal sizes, they're not more expensive (but don't buy the "too good to be true" ones) and means not having to deal with entirely unprotected battery terminals eager to give you a Very Bad Time.

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

#79

Post by Saris »

hinkley wrote: post #47
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 statio…

There's usually a pretty big gap in time between 'worn' at say 70-80% of original capacity, and a pack that has actual failed cells in it too.

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

#80

Post by robofunk »

What's interesting is that if the batteries are being sourced from JDM cars the batteries are probably relatively young due to the average age of Japanese cars being relatively low (8.7 years) and the amount of yearly mileage is also half for JDM cars when compared to the US. So if you tried the same in the US it may not be as viable.
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