Starting from scratch
When starting with the BMS we were a group of 4 people in the powertrain team. None of us had prior experience with designing a BMS before.
Our first task was to establish an outline of the BMS. Should we buy one or build a BMS ourselves? How complex should we allow the BMS to be? How will the BMS fit together with other systems?
Eventually we settled on a master-slave design where a single master processor controls a set of 12 daisy-chained sensor slave boards. Each slave board measures the temperature and voltage of 12 lithium-ion cells and is no longer than a medium sized ruler.
The powertrain team has also been responsible for making two PCBs outside of the battery container. These were the Vehicle Control Unit (VCU) and the Traction System Active Light controller (TSAL). The VCU is a board that works similar to how the throttle works on a fuel driven car, i.e., it restricts motor power depending on the input of the driver.
The TSAL controller has the duty of informing the driver if our traction system is in a safe state using a standard LED-light.
In total, we have bought over 20 PCBs from Eurocircuits; we are happy and satisfied with the quality of the PCBs. Shipments were fast which was very appreciated during the prototyping phase.