How many batteries / "power cells" will I need to...

[helotaxi 5,000+ posts]

The most efficient way is to leave the engine running. Think about how much gas you could buy for the money you are thinking about spending to be able to turn the engine off.

 

[infamous_e46 5,000+ posts]

http://www.caraudio.com/forums/car-audio-classifieds/491688-optima-d31ts-big-yellow-tops-brand-new.html

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[phuck CA.com 10+ year member]

buy a remote start/kill system for the car. cost less then 5 batteries. the car will run for up to 60 minutes depending on the system. Some are programmable. if you are at a show and some ahole tries to snatch the car you hit a button and shut it off.