Compressors draw an awfull lot of power from engines. Here's a link to a site where a guy built a air conditioner for his electric vehicle. An plastic ice chest, 12 battery, Ice water, a pump, tubes, wires, 2 fans, and a heater core was all it took.
Really cool website and a great invention. So you can ride in comfort without running the compressor.
BTW, its 8 degrees F outside right now and I'm talking about air conditioning. Sheesh.
http://www.instructables.com/id/Port...eap-and-easy!/