The 7S 25.9V 18650 Lithium Battery Equalizer Board 29.4V Polymer Battery Equalizer Board Connector is designed to balance the voltage between cells in a 7-series battery pack. It ensures stable performance, prevents overcharging or over-discharging of individual cells, and extends battery lifespan. Ideal for lithium-ion and lithium polymer battery packs used in electric vehicles, solar storage, and DIY energy projects.