Read last summer about using portable fans in the car. To assist before the a/c takes over. Too hard on the battery? I saw 12volt mini car fans. Also could it be helpful in reducing the a/c draw when driving even?
I often use a thermoelectric cooler in my Prius. It handles a 4-5 amp load with no problems except a little heating of the connector. Just make sure that your accessory doesn't draw significantly more current. JeffD
