I Put the biggest 12 volt battery I could in my kids 6 volt power wheels corvette and jeep. I had to screw bicycle tires to the rear wheels because they were spinning the plastic wheels to the point of melting the plastic. They could pop and ride wheelies. The corvette was geared for speed (full sprint to stay with it)while the jeep could climb any thing in its path. The kids put thousands of hours in them around the property over many years. They were the cool kids in the neighborhood. I told them if they ever drove in the road that their power wheels would be gone for ever. They were careful not to test me on that.