Battery Management System (BMS)
A battery management system (BMS) is the electronics and software that supervise an EV battery pack. It monitors values such as cell voltage, pack current, and temperature, then uses those measurements to keep the battery within its permitted operating limits.
What it does
The BMS estimates state of charge and battery health, controls or requests contactor operation, and coordinates charging, power delivery, and thermal management. It can reduce charging or propulsion power when conditions require protection. Because state of charge cannot be measured like liquid in a tank, the displayed percentage is a calculated estimate informed by sensors and battery models.
The BMS is one part of the vehicle's complete high-voltage control system; its exact functions and safety strategy vary by design. See Battery Management System for a deeper explanation of monitoring, balancing, protection, and communication.