Effects of stack pressure on the equivalent circuit model of lithium-ion batteries

The stack-level mechanical pressure is inevitable in battery pack and it has a significant effect on battery characteristics. However, parameters variation of equivalent circuit models (ECMs) caused by stack pressure has seldom been considered. For the first time, the effect of stack pressure on ECM is investigated in detail with commercial Li[NiCoMn]O2 (NMC) cells and LiFePO4 (LFP) cells in this paper. The changes in model parameters and their influence on model accuracy are evaluated through a test procedure including capacity tests, a modified Hybrid Pulse Power Characteristic test, and the dynamic current test. The results of the comprehensive experiments show that all the parameters of ECM vary significantly with stack pressures. Voltage errors in model simulations suggest that the pressure-induced parameter differences reduce the model accuracy. To further demonstrate the effects, the SOC estimation is carried out, which indicate the negative impact of such parameter variations on model application. These results are instructive for the application of the ECM in battery management.

Automated summary

This paper investigates the effects of stack pressure on equivalent circuit model parameters of batteries. The study evaluates the changes in model parameters and their impact on model accuracy through various tests. The results show that stack pressure significantly affects all model parameters and reduces model accuracy. These findings are instructive for the application of equivalent circuit models in battery management.