University of Canterbury Motorsport (UCM) is a student run club from Christchurch, New Zealand that designs and builds race cars to compete in the international Formula- SAE competition. In 2023, University of Canterbury Motorsport won the Formula SAE Australasia competition with a car that departed significantly from the team’s previous vehicle designs.

Since 2016, University of Canterbury Motorsport has built EVs, with incremental improvements each year. The 2023 car, named UCM23, featured the team’s first custom designed Battery Management System (BMS), a critical sub-system in the car’s high voltage battery pack.

The author was responsible for overall technical direction of the UCM23 programme and developed a completely new BMS for the car. This BMS was designed to comply with Formula SAE rules to ensure the safe operation of the car. In addition, features to strategically manage the vehicle’s efficiency and improve ease of operation were developed.

UCM23’s battery pack is constructed from Sony/Murata VTC5A cells, of a cylindrical 18650 form factor. These cells are assembled to form UCM23’s battery pack, in a 96s5p configuration. This pack is 403V at full charge, with 4.5kWh of energy storage. UCM23’s battery pack is monitored by eight BMS modules, that report via a CAN bus to a control unit. Each BMS module manages 12 series connected cells. These modules are designed around the LTC6811 Battery Management IC (BMIC), providing the analogue front end. The voltage of each series connection and the temperature of the respective cells is measured by the BMS. These measurements provide immediate information on the health of each cell, and are used to trigger a shutdown of the car if a voltage or temperature exceeds hard operating limits. Over time, these measurements are used to determine the overall State of Health (SoH) and State of Charge (SoC) of the battery pack.

Development of UCM23’s BMS was divided into two phases, prior to and following the 2023 Formula-SAE Australasia competition. Prior to the competition, development was aimed at establishing reliability of the essential functionality required by the competition rules. Following the competition, a significant portion of the system’s software was rewritten, learning from the initial implementation, and aimed to ease implementation of more advanced algorithms. During this latter phase, a SoH algorithm was developed and more advanced SoC algorithms were implemented.