Demonstration circuit 2043B is a lead-acid battery balancer featuring the LTC3305. The LTC3305 balances up to four lead-acid batteries connected in series and incorporates all voltage monitoring, gate drive and fault detection circuitry. The LTC3305 employs an auxiliary battery or an alternative storage means to transfer charge to or from each individual battery within the stack. There are two operating modes, TIMER mode and CONTINUOUS mode, selected by the MODE pin. In TIMER mode, once the balancing operation is complete, the LTC3305 goes to a low power state for a programmed time and then periodically rebalances the batteries. In CONTINUOUS mode, the balancing operation continues even after the batteries are balanced to their programmed termination voltage.