Patent ID: 8922166

Claim:
An apparatus, comprising: a first battery pack system module, comprising: a first terminal; a second terminal; a first plurality of battery cells in communication with the first terminal and the second terminal; a first charge switch in communication with the first terminal and the first plurality of battery cells, in which the first charge switch, when activated, physically disconnects the first plurality of battery cells from the first terminal to prevent charging of the first plurality of battery cells; and a controller configured to: detect that the first battery pack system module has reached a first state of charge; activate the first charge switch to physically disconnect and to prevent further charging of the first battery pack system module after detecting the first state of charge; discharging the first plurality of battery cells after activating the first charge switch to balance the first battery pack system module with a second battery pack system module coupled to the first battery pack system module; de-activating the first charge switch after discharging the first plurality of battery cells; and charging the first plurality of battery cells after de-activating the first charge switch.