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PoLoMoTo t1_j24qijl wrote

Reply to comment by enjoyoutdoors in ELI5 why do electric vehicles have one big battery that's hard to replace once it's expired, rather than lots of smaller ones that could be swapped out based on need (to trade off range/power/weight)? by ginonofalg

To add on to this, yes some cells will die before others but in general when the battery pack is nearing the end of its life none of the cells are going to be very good anymore and you'd probably end up replacing all of them anyway. Additionally combining brand new cells with old worn cells is probably not a great idea for balancing.

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sold_snek t1_j24xoq9 wrote

I remember seeing a case where Tesla was charging wild money to replace a battery and the dude paid another company to look it over. While still expensive, it was a lot cheaper for the guy to go battery by battery and find the bad batch then replace it and car was good again.

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PoLoMoTo t1_j24z9ee wrote

I have no doubt that would work but I would be curious as to the longevity of that. Also if it was a high mileage battery or some fluke internal failure, and what percentage of the cells they actually replaced. I'll have to try to find the story sometime.

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greatvaluemeeseeks t1_j25e83m wrote

A few companies do this with Prius batteries and sell them as refurbished batteries. The cells aren't too hard to disassemble and a dead cell is pretty easy to isolate. A refurbished battery is much cheaper than a brand new one from Toyota, but the batteries don't last very long before another cell eventually dies since they probably have 150k+ miles on them and Toyota, in my opinion, provided inadequate cooling for them and should have told consumers the battery's cooling system required regular maintenance.

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Lyrle t1_j26gnwi wrote

Rich Rebuilds had an episode like this. The car featured there was not very old.

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ikingrpg t1_j261dqp wrote

Yeah, that was a rare case where the car wasn't that old, but one cell just went bad. You wouldn't want to do the same thing if all the cells were old.

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Bensemus t1_j2co8yg wrote

This is just the difference between dealership repairs and independent garage repairs. Tesla isn’t interested in diving super deep and doing a one off fix. They do high level repairs which cost more.

It also shows that Teslas aren’t locked to Tesla like so many claim. You can bring it to other people to get it fixed.

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sold_snek t1_j2csqgs wrote

> You can bring it to other people to get it fixed.

You need literal electrical engineers to do it and Tesla won't touch your vehicle afterward. It's a pretty big cost to do anything outside of Tesla.

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rickymilby t1_j25y914 wrote

This is correct, you can't mix new batteries and old batteries as it is impossible to balance.

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