Thermal behavior of intelligent automotive lithium-ion batteries: Experimental study with switchable cells and reconfigurable modules

Abstract

Conventional battery systems are limited regarding safety, reliability and aging performance due to fixed configurations. Intelligent battery systems are a promising solution with switches at cell level that allow adaptive reconfiguration of the system. However, the thermal influences of electronics and bypassing procedures of such systems are unknown up to now and need to be quantified. In this work, a hardware prototype of a switchable cell is realized with a 25Ah prismatic automotive cell. The impact on the temperature on cell level for challenging 6C discharge conditions is investigated experimentally revealing small electronics losses due to the design. Combining 12 cells in an intelligent module prototype, the thermal module behavior is investigated in terms of serial/parallel topology and effects of reconfiguration procedures. For the first time, the thermal effects in an automotive environment are tested for cells or strings being bypassed permanently during operation. Due to the thermal coupling in modules, even bypassed cells reach 40%–60% of the temperature of normally operated cells. Thereby bypassing in a parallel module is revealed to have far more thermal influence than in a serial connection.