As others have noted, there were quite a few reports in the Soul topic and on that forum about excessive battery degradation in heat, and IIRR AVTA also found that the Soul wasn't much better than the LEAF, at least in Phoenix. The master page for all those tests is here: https://avt.inl.gov/vehicle-type/all-po ... ure?page=1
Unfortunately there seems to be a problem with the individual pages at the moment, but here's an old post from the Soul topic that references the results after 11 months: https://avt.inl.gov/vehicle-type/all-po ... ure?page=1
In short, the only ATM method that seems to have a major effect on degradationis liquid cooling, and even that has to be well done - Ford's for the Focus apparently wasn't (the set temp for cooling was apparently too high), but GM's and Tesla's were, and I forget how BMW fared. I'd expect the current Korean battery packs, which do have liquid cooling, to do better than the 1st gen. Soul.
OT: In my ICE I normally don't use the A/C until the car's OAT gauge is over 84 degrees and that will be sustained for at least 20 minutes or more, but on my recent trip up to Mt. Shasta and back, along the Central Valley in I-5, I was curious on the way back to see just how high a temp would be reasonably comfortable using only the fan. Note - I bought my first car with A/C back in the '80s specifically to deal with high Central Valley summer temps, as I'd done enough sweltering in non-A/C equipped cars while driving across or along it.
Anyway, I found that shirtless, just wearing shorts and sockless sandals (my normal hot weather driving attire, and with cloth seats which I insist on), I was OK right up to the car's OAT gauge reading 100 briefly. It was between 93 and 99 from Redding all the way down I-5 to Dunnigan. Note, this isn't the official shade
temp, and it was actually a relatively cool summer afternoon by Central Valley standards. It's also dry heat, so there's no comparison to areas with similar temps and high humidity. But the heat was
making me drowsy (and I'd been awake since around 1 a.m. and this was mid-afternoon), so after seeing 100 for a brief period around Red Bluff I turned the A/C on and was a lot more alert, not to mention happier!
One noticeable advantage of a PEV over an ICE is at rest stops in high temps. I got so drowsy that I still needed to needed to pull off and take a nap at the Dunnigan rest area, but this is difficult/impossible for me in high temps, and leaving the engine idling to run the A/C while I'm trying to take a nap isn't something I want to do. A PEV could just run the A/C while it was charging, and this wouldn't be an issue. End OT.