←back to thread

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

(www.thedrive.com)
304 points computerliker | 5 comments | 23 Aug 25 18:29 UTC | HN request time: 0.021s | source
Show context
zhyder ◴[27 Aug 25 17:50 UTC] No.45042740[source]▶
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 module used a lot at its EOL, thereby making EVs last longer and be viable as cheap used cars even past 10 years like ICE cars are

3) Allow easier upgrades as chemistry improves: solid-state, sodium ion, etc.

Modules could be electrically tested for fit. I'd think the fit range would be quite wide (e.g. if one supported lower max discharge rates than another) given the headroom we have with EVs' power these days: they have far-more-than-needed power (which mostly comes for free with EV range).

The tradeoff is that they'd need to be built to be modular with some standardization on module dimensions (maybe we'll have "ZZ" size like we have AA, C, etc today), and would take a tad more volume in the vehicle (though the limiting factor is weight rather than volume). Easily worthwhile over the current model with a huge monolithic pack.

replies(9): >>45042833 #>>45042894 #>>45042908 #>>45042938 #>>45043196 #>>45043239 #>>45043635 #>>45044625 #>>45046054 #
1. stetrain ◴[27 Aug 25 18:27 UTC] No.45043196[source]▶
GM claims that this is exactly how their Ultium battery pack architecture works. It is made up of multiple modules each with their own BMS, and supposedly one module can be replaced without having to be a match in chemistry and degradation to the other modules.

I'm unsure if that will actually work so well in practice, where you still need to charge all the cells simultaneously when doing DC fast charging etc.

Also all of that extra architecture adds cost and complexity to each vehicle that rolls out the door, compared to a pack that just packs in a bunch of cells together with the necessary cooling etc. as one contiguous unit.

Given that EV battery packs in the real world are trending to last longer than the cars they come in, going with a simpler pack design and swapping in a refurbished pack if you experience a premature failure might be the more economical route.

replies(1): >>45044835 #
2. hinkley ◴[27 Aug 25 20:33 UTC] No.45044835[source]▶
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%.
replies(1): >>45045251 #
3. stetrain ◴[27 Aug 25 21:03 UTC] No.45045251[source]▶
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?
replies(2): >>45045519 #>>45046691 #
4. hinkley ◴[27 Aug 25 21:29 UTC] No.45045519{3}[source]▶
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.
5. coryrc ◴[27 Aug 25 23:48 UTC] No.45046691{3}[source]▶
I would expect you could only do it with the onboard charger and only if it has one charger per module or the ability to connect the singular charger to each module.