Bidirectional active balancer speeds cell equalization in stacked battery packs
Monolithic Power Systems (MPS) MP2645 is a 5-cell, bidirectional buck-boost active balancer that redistributes charge across series cells with up to 3.75A balance current, using a one-wire stackable interface to scale packs up to 33 series cells.
Passive balancing wastes energy as heat, which slows balancing and can create thermal hotspots in dense packs. MP2645 takes a different approach by moving charge between cells, enabling faster equalization with minimal heat generation, and helping to compensate for cell capacity mismatch to extend runtime in multi-cell battery systems.
A single MP2645 manages charge redistribution across five series cells, supporting chemistries such as Li-ion, Li-polymer, LiFePO4, and even supercapacitors. For larger packs, the active balancer uses a one-wire interface that supports up to eight cascaded devices, providing an easy path to active balancing for multiple series cells without needing complex multi-drop wiring.
This stacking model also helps with modular pack design. Designers can repeat the same 5-cell balancing block across higher-voltage strings, while keeping control and communication simple. The MP2645 is directly powered from the battery cells, reducing the need for extra bias rails or housekeeping supplies in the balancing section.