In conventional batteries, system performance and reliability are limited by the weakest cell. In reconfigurable batteries, the weakest cell can be temporarily or permanently removed from the system. The gained flexibility offers many possibilities for better control and monitoring of the battery system [1]. However, deactivation of individual cells leads to increased power dissipation in the remaining active cells and influences the overall homogeneity [2]. Moreover, the switchable electronics can also cause additional thermal losses [3]. Therefore, the evaluation of the thermal behavior of reconfigurable modules is an important aspect.
In this contribution, the thermal impact of switchable battery cells was experimentally investigated, using a prismatic 25Ah NMC cell equipped with an electronics prototype, which allows the cell to be reversibly activated or bypassed by power switches. Twelve switchable cells were assembled into a module and the thermal behavior of the reconfigurable module was evaluated for two different configurations (12s1p and 4s3p) [2]. Thereby the influence of bypassing individual cells on the temperature distribution in the different module configuration was analyzed. The results show, that the temperature of the module can be actively influenced by bypassing of single cells. Thereby, even though a bypassed cell does not generate heat, the cell-to cell coupling in the module as well as the current flow in the electronics lead to a temperature increase of bypassed cells. In the 12s configuration, bypassing a single cell results in a small decrease in temperature of the bypassed and neighboring cells. Whereas, in case of bypassing a complete parallel string large heat generation and reduced operation time are apparent.
References:
[1] Komsiyska et.al., Energies 14(18) (2021) 5989.
[2] Kleiner et.al., Journal of Energy Storage 44 (2021)103274
[3] Kleiner et.al., IECON 2020 The 46th Annual Conference of the IEEE Industrial Electronics Society, (2020), 2081