A single IC, stand-alone multicell battery balancer for 12V lead acid batteries has been introduced by Linear Technology. To balance battery charge, the LTC3305 absorbs charge from higher voltage batteries and transfers it to lower voltage batteries. Charge is transferred using a lower capacity battery that is sequentially connected across the batteries in the stack. When absorbing charge, the battery also absorbs energy, adding to the total energy in the stack and increasing capacity.
The balancer features sequencing, drive circuitry for high voltage external NFETs, voltage monitoring and protection. Designed for stand-alone operation, the device does not require an MPU or other control circuitry. With the LTC3305, one battery in the stack can be replaced and balanced to the remaining batteries. Suitable applications include telecomm backup systems, home battery-powered backup systems, EVs and industrial lighting systems.
To transfer charge to or from each individual battery in the stack, the balancer utilises an auxiliary battery storage cell. The device features a mode pin, which provides two operating modes: timer mode and continuous mode. In timer mode, once the balancing operation is completed, 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. To balance higher voltage series battery packs, devices can be added to the stack.
The LTC3305, which is offered in a thermally enhanced 0.75mm 38-lead TSSOP, is available now in E and I grades with an operating junction temperature range of -40 to +125°C. The balancer is priced at $6.95 and sold in 1,000-piece quantities.