Selected Cyrusher RD-100 Green Shimano M310 ALTUS Full Suspenion 24 Speeds Folding Mens Mountain Bike Bicycle 17 in 26 in Aluminium Frame Disc Brakes Connect charger with battery first, then connect to wall socket. It will avoid sparks. Avoid empty power, charge when the battery has 30% to 40% power off. Use pedal assistance when the bike is under high current discharge, including heavy weight carrying and up hilling.