Current Imbalance in Parallel Battery Strings Measured Using a Hall‐Effect Sensor Array

Individual cell currents in parallel connected battery strings have been measured using micro Hall‐effect sensors. Cells are routinely connected in electrical series and parallel to meet the power and energy requirements of automotive and consumer electronics applications. Cells connected in series have been extensively studied, however, cells in parallel are often assumed to be a ‘black‐box’ in battery management systems. Poor pack design can result in positive feedback between current and temperature differentials along the parallel string driving greater levels of heterogeneous behaviour and uneven degradation. In this work, a non‐invasive multi‐sensor array board using Hall‐effect sensors is used to individually record the current passing through 8 parallel connected cells in two different electrical configurations, showing highly heterogeneous current distribution. Characteristic ‘waves’ of current and temperature are found to propagate along the parallel battery string and cell rebalancing was found to occur over hundreds of seconds with individual cell currents of up to 1C rate