should drop bugger all yea cable does have some resisitance but hell unless it goes around the car 8 times i doubt it should make a diff. deep cycle are made to discharge and charge alot (have much thicker lead plates) , but this means it dont have as much cranking amps , and seeings as your car is only usuing power when running , the altenator supplies all the power anyhow , id say so gellcell and put a main line fuse near the batt somewhere incase it somehow earths out and decides to put 400 odd amps through the cable in 1/4 of a second