The LTC3305 standalone multi-cell battery balancer works with as many as four 12V lead acid batteries in series. The device does not require a microprocessor or other control circuitry and employs an auxiliary battery storage cell to transfer charge to or from each individual battery in the stack. A mode pin provides two operating modes: timer mode and continuous mode. In timer mode, once balancing is complete, the LTC3305 goes into 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. Available in a thermally-enhanced, 38-lead TSSOP, pricing for the LTC3305 starts at $6.95 each/1,000. A datasheet is available at http://www.linear.com/product/LTC3305
Linear Technology Corp.