The control of the battery pack will be based on the cells, the pack design and the application. From this an envelope will be created where the pack can deliver fully on it’s power and energy demands. Outside of this normal operational window the BMS will control the pack in a number of ways.
If the pack is too cold then the BMS is going to ask for heating. If that is not available then the battery pack is likely to be restricted in performance.
Cell temperature is a critical parameter.
If the cells are getting too hot and in danger of breaking down the control system will open the contactors.
The main reasons for an emergency shutdown are:
- Cell Temperature
- Cell Voltage
- Over Current
- Impact
- Disconnected HV
- User request
A System Engineer’s Thoughts on Contactor Control
Contactor Control is another one of those areas where responsibility is divided between a vehicle’s system level control and the battery management control. From the systems engineering perspective;
- The vehicle system should decide when the contactors are requested to open or close
- The battery management should decide if it can open or close the contactors