The charger that comes with your bike has internal controls that prevent overcharging of the battery. First, plug the charger into the battery. Then connect heck the wire connections at the charger block to and make sure the cord is fully seated. T, and then plug it into a 120v AC outlet. The light on the charger should be RED, and that light will change to GREEN when the battery is fully charged. We do not recommend leaving the unit plugged in for extended periods of time.
In addition, we do not recommend using the charger unit in poorly ventilated spaces such as closets or drawers, as it may overheat.