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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

#121

Post by DanielHB »

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.

Balancing multiple battery packs at different wear levels is a huge nightmare. You have to run rebalancing operations all the time and on used packs it can be quite dangerous to trigger a thermal runaway.

If they do it with different types of batteries it is even more complicated, like you need to write some custom software to sync all that up. This is not a trivial project.

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

#122

Post by 542354234235 »

TGower wrote: post #85
zhyder wrote: post #4

Neat idea to mix batteries of different age and chemistries. I've wondered why EVs couldn't do that too with some power electronics and SW. If an EV battery could have multiple such modules, it'd: 1) Make it easier to carry a cheaper lighter less-natural-resources-consuming battery most of the time. Go to some "gas station" to rent and add more modules when taking a road trip 2) Make it cheaper to replace the 1 modul…

A few tradeoffs you might not be considering: EV battery packs operate at voltages that are seriously hazardous. Consumers coming anywhere near those plugs is a non-starter, so even more bulk, weight, and complexity would need to be added to make the installation process foolproof. Waterproofing is critical, the mechanism has to work flawlessly over insertion/removal cycles to keep a watertight seal.

Also, you lose the ability to mold your battery along the bottom of the car, using dead space and keeping the center of gravity low. Gas tanks aren't even boxes, they are molded to fit around other parts with no dead space. So, add that space efficiency loss to all the additional space needed for access panels, installation foolproofing, additional waterproofing, etc.

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

#123

Post by rojcyk »

DanielHB wrote: post #121
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.

Balancing multiple battery packs at different wear levels is a huge nightmare. You have to run rebalancing operations all the time and on used packs it can be quite dangerous to trigger a thermal runaway. If they do it with different types of batteries it is even more complicated, like you need to write some custom software to sync all that up. This is not a trivial project.

So? They considered it to be worth while for them. Thus are working on it.

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

#124

Post by 542354234235 »

rubyn00bie wrote: post #24
zhyder wrote: post #4

Neat idea to mix batteries of different age and chemistries. I've wondered why EVs couldn't do that too with some power electronics and SW. If an EV battery could have multiple such modules, it'd: 1) Make it easier to carry a cheaper lighter less-natural-resources-consuming battery most of the time. Go to some "gas station" to rent and add more modules when taking a road trip 2) Make it cheaper to replace the 1 modul…

I hadn’t thought about different sizes/weights but this does remind me of Nio’s battery swap network. Which I’ve always been fond of in principle. I think at some point in the future, when range isn’t such a competitive advantage in the EV space we’ll see a push towards standardization and something like this will likely occur. I’d guess something around the 1000 mile mark for an EV. Absurd, yes, but at that point no…

It feels like Neo is the opposite of where things should go. The great thing about EV is that every outlet is a refueling station. More EV charging for apartment buildings and parking lots feels like the answer. Those battery swap stations are insanely complex and expensive, and the complexity and added weight on the car are very significant. Unlike a gas station that just needs two nozzle types, or an EV charging port standard, having to standardize battery packs for everything from compacts to trucks would be a nightmare. Most people are not taking hundreds of mile road trips most of the time. Slow charging your car while it sits at home or at work or at the shop will work for 90% of cases. I could see the case for industrial or work vehicles, where keeping them running constantly is a legitimate need, but for personal vehicles that sit in driveways, parking lots, or garages 80% of every day, battery swaps feel like massive overkill.

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

#125

Post by DanielHB »

rojcyk wrote: post #123
DanielHB wrote: post #121

Earlier quoted context omitted.

Balancing multiple battery packs at different wear levels is a huge nightmare. You have to run rebalancing operations all the time and on used packs it can be quite dangerous to trigger a thermal runaway. If they do it with different types of batteries it is even more complicated, like you need to write some custom software to sync all that up. This is not a trivial project.

So? They considered it to be worth while for them. Thus are working on it.

I know, it seems it is fairly large operation however, if it wasn't I would assume it was a PR stunt.

This is definitely not worth doing for small scale operations. As far as I know there is no generic solution for doing this kind of thing (I used to work in the area, but not directly on the BMS systems).

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

#126

Post by londons_explore »

margalabargala wrote: post #99
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…

Why can you not bypass until the voltage falls to zero? I'm with you aside from that.

If you just close the bypass switch, a large current will flow out of the (dying) cell, making a lot of heat.

You could have a two-way bypass, disconnecting the original cell, but that would cost more. Remember the bypass switch is duplicated for every series cell group (hundreds) and must carry the whole battery current.

Or you could have some kind of slow drain resistor - but then you're back to the time issue.

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

#127

Post by DanielHB »

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…

> How do you achieve this with cells in series?

You don't, if one cell fail you shut off the whole array of cells that is in series. But a pack has several arrays of cells.

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

#128

Post by DanielHB »

elevaet wrote: post #31
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.

Sudden failure in a big battery like these is usually due to a single cell failing, which can usually be replaced and then the battery pack is back to the 70% capacity or whatever. Probably in this context of scale it's worth doing the work of replacing bad cells.

Nobody is out there opening packs and replacing single cells, a battery pack is usually composed of multiple modules and each module can have multiple arrays of cells in series. You shutoff the whole array of cells around the cell that failed and the battery keeps working fine at reduced capacity.

If it happens multiple times in the same module you replace a whole module of cells. The packs can usually be disassembled and parts replaced, but the modules are usually soldered down to prevent/mitigate thermal runaway.

Also you can't mix cells of different chemistry or capacity together in the same module. So really if one fails in a module you replace the whole module. Or, in their case, just keep the module there disconnected until the whole battery fails then you scrap the whole battery pack. I assume it is not worth it for them to do any kind of replacements.

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

#129

Post by CyberDildonics »

hinkley wrote: post #110
CyberDildonics wrote: post #100

Earlier quoted context omitted.

You are talking about cells going bad and they are talking about cells that have less capacity from being cycled, not the same thing at all.

No I’m talking about what warrants putting a pack on the secondary market and they’re being unreasonable. Just being 80% of initial capacity isn’t going to prompt someone to swap the batteries out. A damaged pack will.

There are lots of car battery packs out there on the secondary market for many different reasons. Not every single battery pack is taken out from a good car because it has a bad cell.

they’re being unreasonable

No one is being 'unreasonable' you just started talking about something different.

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

#130

Post by 542354234235 »

wiredpancake wrote: post #94
stanmancan wrote: post #86

Earlier quoted context omitted.

Turns out they're lasting much longer than expected: https://news.stanford.edu/stories/2024/12/existing-ev-batter...

Nope. Why would Toyota even have an abundance of "old" EV batteries to begin with if they "lasted much longer than expected". I have a Toyota Landcruiser from 1990.

Cars get scrapped for many reasons and might not have anything to do with the battery pack. I don't know if you have ever heard of junkyards, but people have been going to them for years to get perfectly good parts from junked or totaled cars. The average age of Japanese vehicles is only 9 years old. Most people don't drive cars to 150,000 miles and beyond. If Toyota is using the batteries from older cars, that by definition means they were still useful batteries on those cars.

I really don't know what to say about your 1990 vehicle comment. Good for you? Just because some people own a classic car doesn't change the fact that more than 99% of classic cars are scrap metal now.

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