An apparatus for operating an external manual battery charger having a first AC power input and a DC charging output. The apparatus includes an AC controller configured to adjust at least one power parameter supplied to the AC power input of the external manual battery charger. The power parameter(s) may be any one or more of AC current, AC voltage and AC power. The apparatus further includes a feedback converter configured to monitor at least one charging parameter and to control the AC controller to adjust the one or more power parameters in accordance with the monitored charging parameter or parameters.