The invention relates to a
voltage-equalizing method of the
voltage of all single cells in the
lithium-
cell group and a device thereof, the device comprises a box body, a
lithium-
cell group and an electrical circuit board that is provided with an
electronic switch component, an energy-storing element, a sampling
electronic switch and a
single chip. The
electronic switch component consists of a group of electronic switches with one end respectively communicated with an
electrode leading pin that is formed by the serial connection of the single cells, and with the other end communicated with a leading pin of a power-storage element and a
signal input / output pin of the
single chip. The
single chip controls the on-off of the electronic switches, executes the
voltage sampling of all single cells, closes the corresponding electronic switches as required, takes out and stores the surplus
electric power from the single
cell with higher voltage into the power-storage element so as to decrease the voltage of the single cell, and transmits the
electric power stored in the power-storage element to the single cell with lower voltage so as to increase the voltage of the single cell; under the
automatic control of the single
chip, the
electric power is automatically transferred as required, the voltage of all single cells in the
lithium-cell group becomes equal to realize the voltage equalizing, thereby favoring the energy conversation and improving the service life of the lithium-cell group.