How does not driving a 2010 Prius for long periods affect the hybrid battery?

AC does have some affect, but so does overall battery temperature too. If the sensors detect its over around 110F, i notice it stops charging the batteries until you get to highway speeds. During my morning commute the car works fine, but driving back is middle of the day when sun is the highest, it refuses to charge even when I try to force charge it by pressing brake and gas at same time. The battery volts wont move and it stays at 2 bars. Until i get on the highway and am traveling 60mph, then theyll start charging despite their temp readings. Im going to guess this is a safety feature to help prolong the batteries lifespan. It kills my mpg by a lot, and i have very sluggish acceleration since its strictly just the engine trying to accelerate the car at that point. If you arnt experiencing this, then your batteries are healthy enough.

 

Does the car's AC work? If your AC is running, and it's cool IN the car, the outside
temp doesn't really matter. The intake for the hybrid battery fan is inside the car.