Child's Bike

I just give a small child bike is said to be electric. It has a small engine and a few globes attached here and there. when a button is pressed the wheels spin. It was then that I can hook it to a converter of the wall. My question is, what is the best way to do it himself with the power from him and not a cord mass goes to him a power point!

Is there a place for a battery on this bike? If so, determine the motor voltage is proper and install the battery. I would say it would take a 12 volt battery, but sure. Get a charger and let your child (ren) have fun.