A system and method are described permitting a sophisticated control of a battery composed of a multiplicity of three-terminal electrochemical cells. Each cell has first and second terminals, connected with respective electrodes, one of which is a positive terminal and one of which is a negative terminal. Each cell has a third terminal connected with a grid electrode. A battery is composed of N cells. For each of the N cells, there is provided a respective capacitor switchably coupled to the second and third terminals thereof. A controller is connected through a switching matrix to the capacitors. In operation, the controller is connected sequentially to each capacitor among the multiplicity of capacitors, during which time the capacitor is momentarily uncoupled from its respective cell. When the controller is connected to one of the capacitors, it measures the voltage thereupon. The controller can then charge up or discharge the capacitor to drive it to a desired voltage level. Thereafter, the capacitor is disconnected from the controller and is coupled again to its respective cell.