the r c is what u want in a battery that tells u how long it will discharge a 29 is 210 and a 4d is like 310 that is 1/2 again as long of running time at the same discharge rate. I myself use a little honda generator about the price of 2 good baterries and I can troll all day long on less than 1/2 gallon of fuel. It doesnt scare the fish either like a boat motor.