US Patent 10063068 Battery system

A battery system includes a battery module having first and second battery cells. The battery system further includes first and second cell balancing circuits and a microcontroller. The microcontroller determines a first cell balancing current value indicating an amount of electrical current flowing through a first resistor of the first cell balancing circuit based on the first, second, third, and fourth voltage values and a first resistance value. The microcontroller generates a first fault condition code indicating an operational failure of the first transistor in the first balancing circuit if the first cell balancing current value is less than a minimum desired current value.