Apparatus and method for balancing battery

Battery balancing system according to the present invention, in the plurality of the battery balancing apparatus of a battery pack having a battery, are respectively provided between the plurality of battery to the driving of the switching part of the switching unit to connect each battery, a plurality of batteries and a parallel connection selection circuit section for the two battery is selected by calculating an average value by detecting the voltage for each of the plurality of battery, if the mean value to the reference value, there are balancing target battery after checking the balancing target battery for the maximum voltage of which by selecting the battery and the lowest voltage battery is characterized in that a control unit for controlling said selection circuit to be parallel to each other And, a separate battery balancing method of the invention, according periodically when the balancing target battery a predetermined number exists by detecting the voltage of the plurality of batteries by selecting those of the highest voltage of the battery with the lowest voltage battery in parallel to each other and thereby the external power source of the battery voltage up to a voltage exceeding the average value of the lowest-voltage battery is discharged without the less-than-voltage average value is characterized in that the balancing is completed, as charging. Electric vehicles, hybrid vehicles, battery