Isn't 10.375" x 7.125" x 10.875" somewhat bigger than a PowerWheels battery?If the motors draw 3A at 12V they are likely to draw 1.5A at 6V unless you re-wind the motors to draw more current.
these motors are on powerwheels and this battery doesnt look that much bigger than the batteries that come with it and only last 30 minutes.
How is that compared to a jump starting box. The ones you carry in your car that have 450 cold cranking amps. Are they not a C type battery?