Battery replaced in 2017 Bolt EV

I dropped off my 2017 Bolt EV for recall battery replacement the day before yesterday. When I dropped it off, Torque Pro said I had 55.0kWh of BMS-reported usable energy:

Yesterday morning I confirmed the repair was in progress by noting that I could not remotely connect to the car with the Chevrolet app. I pinged the dealer about pickup in the afternoon and was told the battery was in, but they were waiting on a battery coolant hose they determined needed replacement. The Chevy app showed the car back online and with a different SOC than I dropped it off with. I noted it was showing 21%, which belies the usual guidance for large Li-ion batteries to be shipped at fairly low SOC. Not sure how much difference that makes for likelihood/severity of a real thermal event during transit. There’s still a ton of stored and chemical energy in an EV pack at 20%, or 0%.

This morning I got the call that the hose was on, car was plugged in to charge, and it was ready for pickup. The app confirmed it’s charging.

Thanks Chevy for a free new battery! I am curious what the Torque-reported usable kWh will be when I pick it up. Technical/advertising kWh is 66, usable will be somewhat less. No matter what, it’s a substantial capacity increase from 55kWh.

Excellent! Apparently LG finally fixed their stuff?

The issue isn’t the amount of stored electrical and chemical energy, it’s, “Do you have enough of the first to make the second relevant?”

As a general rule of thumb, lithium is shipped around 40% SoC (3.65V or so is common to see on shipped 18650s). That’s high enough that self discharge won’t drain the cell in any reasonable period of time, but low enough that you don’t have enough energy to get really exciting. Below about 50% SoC for most lithium chemistries, there’s just not enough electrical energy to heat the pack up enough that the chemical energy starts mattering (thermal runaway). At high state of charge, most chemistries will do that, though I believe LiFePO4 can’t quite manage it (it’s a good bit more stable and takes a far higher temperature to enter thermal runaway). LiCoO2 is damned near thermal runaway on a hot day after a good run on an RC plane, so… yeah, don’t us that chemistry if you can avoid it.

In any case, for short term storage/shipping, 20% SoC is definitely low enough to avoid anything particularly nasty happening. Hopefully LG has it fixed, I have considered a Bolt as a pure EV in a decade when we need another car!

Yep! The public-facing statement is that the defect that results in thermal runaway is the rare™ co-incidence of two separate defects, a torn anode tab and a folder separator, that can cause thermal runaway, mostly at high SOC after charge sessions from low SOC.

Ah, interesting. Would it be accurate to say, then, that shorting a typical battery (e.g. LMC 811) at ~30% would result in a battery that is hot but not hot enough to cause thermal runaway? That would make sense. I think there’s a 30% rule out there somewhere, maybe from the DOT? That’s the rule we used at my former EV OEM employer.

4.5 stars, would buy again, good value for money. Could use faster DCFC for interstate travel. New battery a perk!

Good. I knew they were fighting that, and wasn’t sure if LG had actually managed to fix the problem. I gather it was keeping GM and LG engineers working late for a while.

That’s the likely result, yes. It’s going to be hot, unhappy, and probably ruined, but it shouldn’t be hot enough to enter thermal runaway, which then means it won’t be hot enough to propagate thermal runaway. A single cell running away is a problem, but it often enough emits enough heat to get the cells around it to run away too, and that’s when you’re going to have a really bad day.

New capacity: 13% upgrade!

Nice! Though you probably have to cycle it a few times for it to dial the numbers in.

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Probably so. The GM nameplate (rated at 25C) is 66, the LG nameplate is 64 (rated at 20C) and there is some minimal buffer, theoretically all at th bottom and zero buffer at the top according to some research on I drove it straight from the Chevy dealer to Costco to get new tires put on (it was DUE) so Smokey is fit as a fiddle and ready for some Christmas road trips now! Planning a 2000+mi RT trip to the Space Coast area between Christmas and New Year. I am hoping to test/verify the increased fast charging speeds (smooth taper instead of stepped, more area under the curve) tomorrow if my battery stays warm enough in the garage overnight.

Now I just need to find what’s causing the creak/rattle from the back hatch…