you can use any copper cable that is coated so it does not lay under the battery tray and ground out..... if it does then it will be putting alot of amps through that wire and might burn up or cause a fire.... use some of the plastic coating with the slit down the side to cover it over.... that way the vibration of the wire rubbing on the metal will not rub off the insulation and cause a spark, fire or shoring....
