Battery pack charging system and its control method and apparatus, control unit, and storage medium

The present application discloses a battery pack charging system and its control method. The battery pack charging system includes a battery pack, a charging apparatus, a negative pulse absorbing branch, and a control unit; the negative pulse absorbing branch includes a switch, a power resistor connected in series with the switch, and a supercapacitor connected in series with the power resistor; and the control method includes: monitoring an SOC value of the battery pack in a negative pulse charging process for the battery pack; when the SOC value increases by a preset value, controlling the switch to be closed so that the power resistor and the supercapacitor can absorb discharge energy of the battery pack; and after the closing time of the switch lasts for a preset duration, controlling the switch to be opened so that depolarization speed in the negative pulse charging process may be increased.