A battery management system allows users to monitor individual cells within a battery pack. As cells work together to release energy to the load, it is crucial to maintain stability throughout the whole pack..
A BMS allows for constant monitoring, gathering, and communicating information to an external interface where users can observe the status of each cell and the health of the battery pack as a whole.
What does a BMS measure?
A BMS can measure different figures such as current, voltage, temperature, and coulomb count. With these measurements the system can assess the health of the battery and readjust operations as needed to protect the pack.
- State of charge (SoC) and state of health (SoH) are important indicators for assessing the usability and capabilities of a battery.
- In electric vehicle batteries, the SoC is used to determine the remaining range left of the car before it needs to be recharged.
- Taking into account charge acceptance, internal resistance, voltage, and self discharge, SoH is an estimation of how much longer a battery can operate optimally.
Why is a BMS important?
Not only is a BMS important in indicating the health of a battery, but it also functions to protect the battery while in operation.
Each battery cell and chemistry has voltage, temperature, and current range within which it can safely operate. When a cell drops below or exceeds these ranges, it can be detected and controlled by the BMS. For instance, lithium is a highly reactive substance; thus the BMS should monitor each lithium cell to ensure that it remains operating within predefined limits. This keeps the battery safe and preserves it in the long run.
Another important safety feature of a BMS is cell balancing. Individual cells within a battery pack do not operate equally. One cell may be weaker or stronger than the other, charging or discharging faster than others within the chain. Without proper compensation, this could degrade the health of the overall pack. If one cell short circuits or fails, this affects the stability of the whole pack. Cell balancing equalizes the charge between individual cells based on each cell’s capability. The BMS helps to monitor and control the charge demanded from each cell in the chain, ensuring that SoC remains evenly distributed.