Balancer Efficiency Matters!
One of the biggest enemies faced by a battery pack is heat. High ambient temperatures rapidly degrade battery lifetime and performance. Unfortunately, in high current battery systems, the balancing currents must also be high in order to extend run times or to achieve fast charging of the pack. Poor balancer efficiency results in unwanted heat inside the battery system, and must be addressed by reducing the number of balancers that can run at a given time or through expensive thermal mitigation methods.
Figure 6 LTC3300 power stage performance
As shown in Figure 6, the LTC3300 achieves >90% efficiency in both the charging and discharging directions, which allows the balance current to be more than doubled relative to an 80% efficient solution with equal balancer power dissipation. Furthermore, higher balancer efficiency produces more effective charge redistribution, which in turn produces more effective capacity recovery and faster charging.
Local Cells Do Most of the Balancing Work
Transferring charge throughout the stack is achieved by interleaving the secondary side connections as shown in Figure 7. Interleaving in this manner allows charge from any group of six cells to be transferred to or from a group of adjacent cells. Note that the adjacent cells may be either above or below in the stack. This flexibility is helpful when optimizing a balancing algorithm. A common misconception with any interleaved system is that redistributing charge from the top of a very tall stack to the bottom must be horribly inefficient due to all