A charging system comprising a power supply device and a device to be charged, wherein the power supply device is a power supply device with adjustable output voltage and is configured to be controlled to output a pulsating direct current, the device to be charged comprising: a battery; and a battery management circuit, the battery management circuit comprising a first charging channel, an equalization circuit, and a communication circuit, the first charging channel being configured to receive charging voltage and/or charging current from the power supply device and charge the battery, which is a lithium battery, by applying directly the charging voltage and/or charging current to the battery, and the battery comprising a first cell and a second cell coupled in series, wherein the charging current applied to the battery is a pulsating direct current; the communication circuit being configured to communicate with the power supply device to make magnitude of the charging voltage and/or charging current received from the power supply device match a current charging stage of the battery, when the power supply device charges the battery through the first charging channel; the equalization circuit being coupled with the first cell and the second cell and configured to equalize voltage of the first cell and voltage of the second cell; the equalization circuit comprising an RLC series circuit, a switch circuit, and a control circuit, the switch circuit being connected with the first cell and the second cell and having an end coupled to the RLC series circuit such that the switch circuit can form a closed loop with the RLC series circuit and either one of the first cell and the second cell, and the switch circuit having a control end (62, 65, 68, 71) coupled with the control circuit; and the control circuit being configured to control the switch circuit to make the first cell and the second cell alternately form a closed loop with the RLC series circuit to provide input voltage for the RLC series circuit, when the voltage of the first cell and the voltage of the second cell are nonequalized, wherein one single cell is adopted to supply power to the system of the device to be charged. a battery; and a battery management circuit, the battery management circuit comprising a first charging channel, an equalization circuit, and a communication circuit, the first charging channel being configured to receive charging voltage and/or charging current from the power supply device and charge the battery, which is a lithium battery, by applying directly the charging voltage and/or charging current to the battery, and the battery comprising a first cell and a second cell coupled in series, wherein the charging current applied to the battery is a pulsating direct current; the communication circuit being configured to communicate with the power supply device to make magnitude of the charging voltage and/or charging current received from the power supply device match a current charging stage of the battery, when the power supply device charges the battery through the first charging channel; the equalization circuit being coupled with the first cell and the second cell and configured to equalize voltage of the first cell and voltage of the second cell; the equalization circuit comprising an RLC series circuit, a switch circuit, and a control circuit, the switch circuit being connected with the first cell and the second cell and having an end coupled to the RLC series circuit such that the switch circuit can form a closed loop with the RLC series circuit and either one of the first cell and the second cell, and the switch circuit having a control end (62, 65, 68, 71) coupled with the control circuit; and the control circuit being configured to control the switch circuit to make the first cell and the second cell alternately form a closed loop with the RLC series circuit to provide input voltage for the RLC series circuit, when the voltage of the first cell and the voltage of the second cell are nonequalized, wherein one single cell is adopted to supply power to the system of the device to be charged.