Cell potentials and temperatures are kept within safe ranges.

Figure 1 is a simplified block diagram showing (1) a high-power rechargeable battery comprising multiple series-connected modules, each module containing multiple series-connected rechargeable cells, and (2) a system for monitoring battery voltages and controlling the charging of the battery. To ensure safe, reliable operation of the battery, it is imperative to ensure that the potentials and temperatures of all the cells remain within prescribed limits. Accordingly, the system monitors the potential of each cell, the overall potential of each module, and the temperature of each cell. Because overcharging can damage a cell, if the potential of any cell exceeds a predetermined maximum allowable level, the system interrupts the charging process and starts another process, called “equalization,” in which the affected cell is partially discharged through a resistor until its potential reaches a prescribed safe lower level. If the temperature of any cell or module exceeds a predetermined maximum allowable value, or if a fault is detected, the system stops the charging process.

Figure 1. Modules Containing Cells in Series are connected in series to a charging subsystem, and the cells in each module are connected to monitoring and control circuitry on a battery-control board.

The operation of the system as a whole and the operations of the battery-control boards are coordinated by a control computer. The processors on the battery-control boards communicate with the control computer via a network than can be of any wired or wireless type commonly used for communication among computers.