Abstract: A battery management system for the propulsion batteries of an electric vehicle comprises means for voltage sensing, temperature sensing, voltage limit sensing, and current limit sensing. Charge control is employed for optimal system operation and ensures cell balancing by detecting the lowest charged cells in a cell stack and charging those cells first, thereby ensuring that all cells charge uniformly. Charge control is accomplished on a battery management circuit board associated with battery cells in a battery box, while control of the battery management board is governed by a system controller board through a controller area network interface. The system controller board uses data from the battery management board to govern charge characteristics of the batteries, and supply data and control functions to a driver interface computer.

Abstract: A method of balancing the terminal voltage across individual and multiple battery cells is described. To employ the method a lithium ion battery having at least two battery cells is provided along with an energy dispersing unit capable of taking energy from individual cells, stepping down individual voltages, and redirecting the voltage to the lowest voltage battery cell. The terminal voltage of individual cells is then monitored during discharge, and discharging cells having a greater terminal voltage are discharged in advance of cells having less terminal voltage. Thereafter establishing a charge algorithm wherein a differential curve is established under specific conditions, and charging current is applied complimentary to the differential curve.