A power management system includes a battery charging system, a power supplying system, a first switching module, and a second switching module. The power management system is switched between the battery charging system and the power supplying system via the first switching module and the second switching module. With a charging electric energy generated by the waveform generating module, the battery charging system could restore the aging battery or the battery with degraded performance to a better state when the batteries are charging. By sensing a battery state of batteries, the power supplying system provides a supplementing power to the batteries, and the supplementing power and a power of the batteries could be supplied to a load together.