A battery charger with an internal power storage device may be used to facilitate fast charging of a battery by using a high C-rate. A battery charger with an internal power storage device may include a control circuit that receives operating mode instructions to operate in a base charging mode or a fast charging mode. In the base charging mode, the battery charger may be configured to concurrently charge a battery and an internal power storage device at a base C-rate using current supplied from an external power source. In the fast charging mode, the battery charger may be configured to charge the battery at a high C-rate, which is substantially higher than the base C-rate, by using the internal power storage device. The battery charger may include an optical reader used to identify battery-specific characteristics and enable the fast charging mode.