Passive Battery Balancing

General Procedure

• Passive balancing discharges the overcharged battery, so all extra power is dissipated as heat in the bleed resistor (in parallel with the cell) and FET (wasted energy).

Open

• When needed, the MOSFET can be turned on to bypass some of the current to the resistor R

• Concern: some power may be dissipated by the MOSFET

• Concern: there is no protection against one cell discharging completely earlier than other cells

Current Calculations

Balancing When Battery Reaches Overvoltage

• The balancing circuit is activated once a cell reaches the overvoltage threshold

• The bypass current must equal the charging current to stop the charging

• It may be difficult to remove the heat

Overall