BMS Deployment Testing
Here is the test of the BMS system before it goes in my car. The BMS assembly is in a CINCH enclosure with the M12 circular connector cables. The image below shows the testing setup with a battery module on the bench. On the left side of the image, you can see one of the one-wire temperature sensors at the end of the cable. That will be soldered to the end of the cable when deployed in the car and attached the battery heatsink surface with some conductive tape. The connections for power and CAN BUS are on a barrier strip that is just off camera to the left. The image shows the BMS with another module I put together to receive the CAN BUS data from the BMS. When deployed in the car the CAN BUS data will be handled by the processor that controls the Instrument Cluster in the dashboard. For testing and the initial deployment, I will use the Data Receiver. It is a BMS PCB with just the CAN BUS circuitry and the Arduino Nano Every installed. It is also mounted in a CINCH enclosure and has the M12 connector for the CAN BUS connection and power. The Nano Every receives the CAN BUS data by SPI from the CAN BUS circuit and then sends the data out via the serial bus, on the USB connector. I wrote a program to read the serial data and interpret the CAN BUS data, which is all in HEX. A screen shot of the application is shown below the battery test image. The application converts the HEX string into decimal values and displays that with a “fuel gauge” graphic for each battery cell. The program can datalog the data to the hard drive. The cell voltage measurement is updated every 2 seconds. The LTC6811-2 BMS IC can be read faster than that but, there is overhead in converting the voltage values to decimal to display. The application also displays the temperature measured from the one-wire probe and the state of charge (SOC). This is the total voltage of all the battery cell voltages added together and is the voltage that is measured on the main battery terminals. The values show the battery in nearly fully charged.
