RE: Battery for Starter box????
Two 7.2 sticks do have more voltage but do not have as much amperage ( which increase torque). If you are trying to start a new .21 engine with two 7.2 volts stick batteries, you will have a much tougher time than you would with one 12V. I have done a conversion on my OFNA Chrome top box so that I can either put two 7.2V's one 12V or power it from my car battery. If I am breaking an engine in, I switch to the 12v or car battery.