HAWKS Racing e.V. - BMS Testing PCB
For our new Formula Student race car, the H21, we developed a completely revised Battery Management System. In particular, the BMS Slave PCBs responsible for monitoring the individual accumulator cells were extensively redesigned.
The main goals of this redesign were to improve the reliability and testability of the system and to comply with the latest Formula Student regulations. Since the BMS is one of the most safety-critical systems in the vehicle, every newly manufactured Slave PCB must be thoroughly tested before it can be installed inside the accumulator.
Testing the boards directly with real battery cells would be unnecessarily complex and could introduce additional safety risks. We therefore developed a dedicated BMS Testing PCB and a corresponding testbench. This setup allows us to verify the electrical functionality, communication and software of every BMS Slave PCB under controlled conditions before it is used in the vehicle.
The outline of the testing PCB is identical to that of our BMS Slave boards. Its mounting holes and electrical contact points are positioned in line with the voltage measurement connections of the Slave PCBs. This allows the individual boards to be stacked on top of each other in a tower-like arrangement.
The boards are mechanically and electrically connected using vertical metal rods. These rods provide the physical connection between the PCBs while simultaneously transferring the simulated cell voltages to the voltage measurement inputs of the BMS Slaves.
A voltage divider on the testing PCB reduces the supplied voltage to approximately 3.7 V per measurement channel. This corresponds roughly to the nominal voltage of the lithium-ion cells used in our accumulator. As a result, the BMS Slaves can be tested under realistic voltage conditions without requiring a complete set of real battery cells.
Below, you can see the assembled testbench with the testing PCB and several BMS Slave boards connected in the vertical arrangement.
Due to the updated regulations, it was also necessary to implement a controlled method for disconnecting the voltage and temperature measurement connections on the BMS Slave boards. This enables us to verify that interrupted sensor connections are detected correctly and that the system reacts appropriately to these fault conditions.
Using the testing PCB, we were able to successfully validate this newly implemented functionality. Individual voltage and temperature measurement channels can be disconnected in a controlled and repeatable manner, allowing us to test the corresponding diagnostic and safety mechanisms without modifying the actual accumulator wiring.
In addition to the hardware changes, new software had to be developed to support the updated placement and configuration of the temperature sensors. The testbench allowed us to simulate the connected sensors and verify that the temperature values were measured, processed and transmitted correctly by the BMS.
The testing setup therefore provides us with a safe and efficient platform for validating both hardware and software. It improves the repeatability of our tests, simplifies troubleshooting and helps us identify potential issues before the BMS components are installed in the accumulator.
We sincerely thank AISLER for their continued support and manufacturing capabilities. Their fast and reliable PCB production enables us to quickly transform our designs into functional hardware and perform several development iterations when necessary.
Without the support of AISLER, the realization and thorough testing of projects such as our new Battery Management System would not be possible.