I moved around country to Florida. Hot weather totally has a toll on the battery. The Prius NiMH battery heats up itself after i park the car at 60%+ battery charge.Sometimes the battery temperature can surge to 120F (Like when i park the car at 70% battery charge). The car will seems sluggish and regen won't work well. This is due to high self discharge rate of NiMH batteries. The Gen 4 lithium battery will do better in hot weather. As you see in the picture, the lithium only has 5 % in 24 hours. The hotter the battery is, the higher the self-discharge rate is. Prius is still awesome. The car handles this hot weather situation well. The battery always cools down quickly after i turn the car back on. I would also drive more on EV before i park to have a lower state of charge before i park.
Wish my HV battery can cool down just only turning engine on. Mine needs engine + all windows up + turn AC for cool air to enter the HV air intake to right of rear passenger seat.
I need to do the same sometimes to make cooling faster. I think as long as the car is on, the battery fan will be on to cool down the battery. Passing cooled air through the vent just make thing faster. Sometimes i hope Prius has liquid cooling for the battery lol.
