A battery cell balancing system , comprising: a plurality of battery cells, each battery cell having a positive terminal and a negative terminal, wherein the battery cells are arranged in series such that the plurality of battery cells has a positive end terminal (B+) and a negative end terminal (B-) disposed on opposing ends thereof; a power supply (no) comprising first and second input terminals respectively connected to the positive and negative end terminals (B+, B-), and first and second output terminals, wherein the power supply configured to receive the cumulative voltage of the battery cells and output a first charging voltage; a charger comprising first and second input terminals respectively connected to the first and second output terminals of the power supply , and first and second output terminals, wherein the charger is configured to receive the first charging voltage from the power supply and to convert the received charging voltage into a second charging voltage less than the first charging voltage; a plurality of pairs of switches electrically connected to the first and second output terminals of the charger, each switch pair configured to be respectively connected to the positive and negative terminals of each of the battery cells; a first ground voltage source electrically connected to the negative end terminal of the plurality of battery cells; and a second ground voltage source different from the first ground voltage source and electrically connected to the second output terminal of the power supply, wherein a switch pair of the switch pairs that is respectively connected to the positive and negative terminals of one of the battery cells that has a voltage less than a reference voltage is configured to be selectively turned on such that the second charging voltage is provided to the battery cell via the turned-on switch pair. a plurality of battery cells, each battery cell having a positive terminal and a negative terminal, wherein the battery cells are arranged in series such that the plurality of battery cells has a positive end terminal (B+) and a negative end terminal (B-) disposed on opposing ends thereof; a power supply (no) comprising first and second input terminals respectively connected to the positive and negative end terminals (B+, B-), and first and second output terminals, wherein the power supply configured to receive the cumulative voltage of the battery cells and output a first charging voltage; a charger comprising first and second input terminals respectively connected to the first and second output terminals of the power supply , and first and second output terminals, wherein the charger is configured to receive the first charging voltage from the power supply and to convert the received charging voltage into a second charging voltage less than the first charging voltage; a plurality of pairs of switches electrically connected to the first and second output terminals of the charger, each switch pair configured to be respectively connected to the positive and negative terminals of each of the battery cells; a first ground voltage source electrically connected to the negative end terminal of the plurality of battery cells; and a second ground voltage source different from the first ground voltage source and electrically connected to the second output terminal of the power supply, wherein a switch pair of the switch pairs that is respectively connected to the positive and negative terminals of one of the battery cells that has a voltage less than a reference voltage is configured to be selectively turned on such that the second charging voltage is provided to the battery cell via the turned-on switch pair. <EOS>