In 35C/95F temp, is it better to charge...

Yeah, I would think neither is ideal, but if I have to choose one, as recommended by Toyota, do the charging in the heat and keep the time fully charged to the minimum. Just make sure you are enabling a battery cooler each time you do charge. No technical reference, but my gut feeling that charging creates heat but battery cooler function can alleviate this. AFAIK, the battery cooler functions only during active charging, not after the pack is fully charged. If heat is detrimental to the battery chemistry, I think the battery cooler functioning during charging in extreme heat may keep the battery cooler than sitting in the extreme heat without the battery cooler functioning. But I might be wrong on this.

BTW, I never had to deal with the heat issue, but the extreme cold issue is mostly solved by having the battery heater function. Toyota warns that a hybrid system may not function during extreme colds, like -40F, but I never had any problem charging the car or operating it in sub-zero temp.

 

I agree. I have seen the battery cooler option display only once in my entire ownership of PP over 4 years. That was during summer over 90F temp and driving the car without AC on for 30 min commuting. Yap, I only saw the display momentarily and could not complete the response, although the charge was done during nighttime and by then the temp was well under 60F, so that was no problem.

Similarly, I find Toyota's way of making the battery heater operator selectable is strange. It should be ON by default, and should not be able to turn off by an operator. I can't think of any good reason not to use the battery heater when the temperature is too low to safely charge the pack.

 

Except for the grill.

 

I have had our 2019 Prime two summers now (the upcoming one will be the third) and I charge at work everyday.

This is in an uncovered area that is southern facing and during the summer, the temps can get to 105 F easily.

When I leave our Prime, I select the "Charge Now" functionality and use the 8 amp setting. This usually takes about 9 hours to fill the battery up.

Since I'm not sure how long I am at work (the joy of being salary and not hourly), our Prime has sat with a full charge in the heat MANY times before.

At 40k miles and charging twice a day I still get 30-32 miles of EV depending on driving conditions, which is consistent with where it was in 2019.

Toyota engineered the car right, so I worry about other things, like how to get a better eco score on the dash board.

Good luck and keep us posted.