A charger circuit which supplies a charging power to charge a battery circuit, includes: a conversion switch circuit, at least one capacitor and a conversion control circuit. The conversion switch circuit is coupled between a charging power and a ground level and includes conversion switches connected in series. The conversion switch circuit has battery voltage balancing nodes electrically connected to the battery circuit, such that each battery is electrically connected between two of the battery voltage balancing nodes. The conversion control circuit is coupled to the conversion switch circuit and provides operation signals to the conversion switch circuit, to respectively control the corresponding conversion switches, so that the capacitor is periodically connected in parallel to each battery of the battery circuit, thereby balancing the battery voltages of the batteries.