DMC designed and built a small scale Battery Management System (BMS) Test Station to be used for demonstration purposes. While the Demo Test Station is intended to be used to demo the capabilities of our larger full scale BMS Tester, it is a fully functioning BMS tester in its own right.
To be able to fully test a BMS, any test platform must be able to accurately simulate a battery pack (to learn more about what this entails, see this white paper). This includes not only the voltages from each of the cells, but any other inputs the BMS module or its sub-modules must read, including inputs from associated temperature, current, and voltage sensors. The BMS Demo Test System was designed to be used with the TI bq20z90 BMS (which only reads voltage differentials from 4 cells, one current sensor, and one temperature sensor with no outputs) but is flexible enough to simulate any battery with up to 6 independent battery cells connected in series, 2 independent current sensors, and 4 variable resistance temperature sensors, while reading up to 3 analog outputs from the BMS under test.
Details of specific subsystems are given below:
Cell voltage simulation: The Demo Test System is capable of simulating up to 6 voltage cells joined in series. Each cell is independently capable of producing 0-7 V and both sinking and sourcing current to accurately simulate charging and discharging conditions.
Temperature sensor simulation: Four variable resistance temperature sensors are simulated using a custom designed temperature sensor simulator board. For this system, components were chosen to allow for 3 predefined temperature settings (hot, room temperature, cold) on each sensor simulator, although the hardware is configurable for as many options as needed.
Current sensor simulators: A BMS must also read in current sensor inputs to determine if a pack is in a charging or discharging state. This demo system was designed to provide two user configurable current sensor simulators.
Voltage and current measurements of individual cells: A digital multimeter and a custom multiplexing solution allows for precise current draw and voltage differential measurements to be made across any two cells in the battery stack as a method to validate all inputs to the BMS.
Analog input sensors: Additionally, after reading all of the inputs available a BMS must be able to communicate externally through a variety of outputs. For this Demo, three analog input sensors are used to read communications originating from the BMS to confirm that the BMS is behaving as designed.