I recently purchased this one from Harbor Freight:

http://www.harborfreight.com/cpi/ctaf/disp...temnumber=95912

connected to just a spare battery, (not one connected to a running vehicle) it pulled my 2000lb Rabbit up the trailer perfectly fine. Started to run out of steam even when the car was flat on the trailer but that was because the battery was dying, so assuming it was connected to a 14v charging source I think it would be even better.

Im not a big fan of HF stuff but for that price I thought it was worth a shot.