Mr. Ors, definitely go with four gauge stranded wire. But more importantly, remember that a battery can explode right in your face and cause serious injury, burns and even loss of eyesight. I would strongly urge you to 1) Learn the correct sequence of connecting. 2) Wear a pair of wrap around good quality eye goggles. 3) Never assume that jumping a battery is without danger. 4) Read the witty but informative tutorial (link below).

Good luck.

http://www.misterfixit.com/jumpstrt.htm

Boone