Design and test of a battery pack simulator

This paper describes the design of a battery pack simulator (BPS). The BPS is an electronic device that emulates all cell voltages of a battery pack in order to test battery management systems (BMS). Cell characteristics and environmental conditions of individual cells, such as capacity or ambient temperature can be adjusted in order to examine the unbalance in a battery pack on the functioning of the BMS. The BPS implements a real time simulation model that comprises interacting electric and thermal submodels. The BPS uses xPC Target and Simulink as real-time software environment. A hardware interface converts all simulated cell voltages and temperatures to real voltages that can be connected to the voltage and temperature sensor inputs of a BMS. We have tested the BPS by comparing the emulated cell voltages of it to the cell voltages of a real battery pack that consists of LiFePO₄ cells. In order to do so, a thermal cell model and third order equivalent network model has been derived by analysing EIS-measurements and pulse current measurements. The found network is implemented in the BPS. Test results show that the maximum deviation between the real and emulated cell voltages is at most 0.5%. We have connected our BPS to a Lithiumate Pro BMS and evaluated the capability to test it with our BPS. We found that basis functionality, like SoC estimation and over and under voltage detection could be tested well. At this moment, the BPS is not suited to test the balancing feature of BMS. Further development of the BPS is needed to enable the testing of this feature of BMS as well.