Abstract: A system for controlling a multi-cell battery having a first set of the cells thereof comprising an active partition adapted for connection to a load and a second set of the cells thereof not connected to the load and comprising a passive partition. Sensors in the cells monitor the temperature, vapor pressure, capacity, pH, current, and voltage of different cells. Signals representative of data values from the sensors are sent to controls which compare it to reference data values and switch cells from the active partition to the passive partition in response to changes in differences between the sensed and reference data values. Cells in the passive partition are recharged from reserve cells. The controls also provide read-outs of the amount of charge remaining in the battery and of the battery's remaining useful life.