When the battery is fully charged but the myoTRACE 400 display does not show 100%, information in its fuel gauge (charge indicator) is outdated and must be revised. The battery fuel gauge is able to learn new settings automatically. To do this you will need to fully discharge and recharge the battery at least two times. To discharge the battery, turn on the myoTRACE 400 and let it run until it shuts off. (A convenient way to discharge the battery is to let the myoTRACE 400 run overnight.) It will take about three to four hours for the battery to recharge. Repeat this a second time. If this solution does not solve the problem, please email Noraxon’s technical support at support@noraxon.com or call (480) 443-3413 (US/Canada customers may call 1-800-364-8985).