What kind of car wash; the ones where the car is pulled along? This requires the car to be in Neutral, free-rolling, and with a Prius this can sometimes lead to hybrid battery being run down. I would suggest: 1. Look for car washes where the car sits and the apparatus moves along. 2. When using pull-along style car wash, leave all the accessories off for the duration, say AC (turn it right off), radio. AC is the big one I think.