Just install a simple 12 volt/120 volt power inverter some new cars have them and most RVs have them.
With one in a car you need to keep the motor running if your using it for something powerful like a power drill. My RV has one 5000 watt inverter running off four deep cell batteries so I can run it all night. I charge them with solar panels on the roof during the day.
$30 to $500 and up
Small inverters plug in a cigarette lighters and over 400 watts need to be hard wired to batteries.
http://www.amazon.com/Powerline-Orig...78887&sr= 1-2
http://www.amazon.com/Black-Decker-V.../dp/B0027ISB1I
http://www.amazon.com/Power-Bright-P...78465&sr= 1-8