A battery pack system comprising a battery pack, a battery management unit, a discharge circuit unit, a charge circuit unit and an energy storage unit, wherein: the battery pack is connected in series with the discharge circuit unit, and the battery pack is connected in series with the charge circuit unit; the battery management unit is connected to the discharge circuit unit, the charge circuit unit and the battery pack, the battery management unit is configured to monitor a temperature of the battery pack and a state of charge, SOC, of the battery pack, send, when the temperature of the battery pack is lower than a first temperature threshold and the SOC of the battery pack is higher than a SOC threshold, a turn-on instruction to the discharge circuit unit to enter a discharging phase, when the discharging phase finishes, stop sending the turn-on instruction to the discharge circuit unit and meanwhile send the turn-on instruction to the charge circuit unit to enter a charging phase, and when the charging phase finishes, stop sending the turn-on instruction to the charge circuit unit and meanwhile send the turn-on instruction to the discharge circuit unit to enter a next discharging phase, so as to periodically send the turn-on instruction to the discharge circuit unit and the charge circuit unit alternately to control the discharge circuit unit and the charge circuit unit to be alternately turned on in each of heating cycles, wherein each of the heating cycles comprises the discharging phase and the charging phase; the discharge circuit unit is connected to the energy storage unit, and the discharge circuit unit is configured to turn on the discharge circuit unit according to the turn-on instruction to enable electricity of the battery pack to flow into the energy storage unit in the discharging phase; the charge circuit unit is connected to the energy storage unit, and the charge circuit unit is configured to turn on the charge circuit unit according to the turn-on instruction to enable electricity of the energy storage unit to flow into the battery pack in the charging phase; and the energy storage unit is configured to store and release electricity; and wherein the battery pack system is characterized in that: a total duration of discharging phases of all of the heating cycles is greater than a total duration of charging phases of all of the heating cycles, wherein the SOC threshold is 30%. the battery pack is connected in series with the discharge circuit unit, and the battery pack is connected in series with the charge circuit unit; the battery management unit is connected to the discharge circuit unit, the charge circuit unit and the battery pack, the battery management unit is configured to monitor a temperature of the battery pack and a state of charge, SOC, of the battery pack, send, when the temperature of the battery pack is lower than a first temperature threshold and the SOC of the battery pack is higher than a SOC threshold, a turn-on instruction to the discharge circuit unit to enter a discharging phase, when the discharging phase finishes, stop sending the turn-on instruction to the discharge circuit unit and meanwhile send the turn-on instruction to the charge circuit unit to enter a charging phase, and when the charging phase finishes, stop sending the turn-on instruction to the charge circuit unit and meanwhile send the turn-on instruction to the discharge circuit unit to enter a next discharging phase, so as to periodically send the turn-on instruction to the discharge circuit unit and the charge circuit unit alternately to control the discharge circuit unit and the charge circuit unit to be alternately turned on in each of heating cycles, wherein each of the heating cycles comprises the discharging phase and the charging phase; the discharge circuit unit is connected to the energy storage unit, and the discharge circuit unit is configured to turn on the discharge circuit unit according to the turn-on instruction to enable electricity of the battery pack to flow into the energy storage unit in the discharging phase; the charge circuit unit is connected to the energy storage unit, and the charge circuit unit is configured to turn on the charge circuit unit according to the turn-on instruction to enable electricity of the energy storage unit to flow into the battery pack in the charging phase; and the energy storage unit is configured to store and release electricity; and wherein the battery pack system is characterized in that: a total duration of discharging phases of all of the heating cycles is greater than a total duration of charging phases of all of the heating cycles, wherein the SOC threshold is 30%. a total duration of discharging phases of all of the heating cycles is greater than a total duration of charging phases of all of the heating cycles, wherein the SOC threshold is 30%.