BMS

A BMS (Battery Management System) is an electronic device that monitors, protects, and manages a battery pack.

Within the VESC ecosystem, a BMS is responsible for monitoring individual cell voltages, pack voltage, current, and temperatures while helping ensure the battery operates safely and within its specified limits.

A BMS can provide a range of functions, including:

• Cell voltage monitoring
• Battery current measurement
• Temperature monitoring
• Cell balancing
• Overvoltage protection
• Undervoltage protection
• Overcurrent protection
• Charge and discharge control
• State of charge estimation
• CAN Bus communication

A BMS sits between the battery cells and the rest of the system, continuously monitoring battery conditions and taking action if a fault or unsafe condition is detected.

Many VESC BMS devices communicate with motor controllers, displays, and other accessories over CAN Bus, allowing battery information such as voltage, current, temperatures, and state of charge to be shared throughout the system.

The VESC Harmony range of BMS devices also integrates a precharge switch and short-circuit protection. This allows the BMS to safely control power delivery to the system while helping protect against damaging fault conditions.

⚠️ A BMS is not a motor controller. A motor controller regulates power to the motor, while a BMS monitors and protects the battery pack.

⚠️ A BMS does not increase the inherent performance of battery cells. Its primary role is to ensure safe operation and help protect the battery from damage caused by overcharging, over-discharging, excessive current, or excessive temperatures. However, upgrading to a higher-capability BMS may allow a battery pack to deliver more of its available performance if the previous BMS was limiting current below what the cells were safely capable of providing.

Cell balancing is one of the most important functions of a BMS. During charging, the BMS can help equalise the voltage of individual cells, improving battery longevity and ensuring all cells remain within safe operating limits.

Example

A VESC Harmony BMS can monitor a battery pack, balance the cells during charging, communicate battery information to a motor controller over CAN Bus, control the precharge process, and disconnect the battery if unsafe operating conditions are detected.

In simple terms: a BMS is the device that monitors and protects a battery pack to keep it operating safely and reliably.