Performance of Passive and Active Balancing Systems of Lithium Batteries in Onerous Mine Environment

To use lithium-iron-phosphate battery packs in the supply systems of any electric mining equipment and/or machines, the required conditions of work safety must be met. This applies in particular to coal mines endangered by fire and/or explosion. To meet the spark-safety conditions, the cells (together with the battery management system—BMS) must be isolated from the influence of the environment, and therefore placed in special fire-tight housings. This significantly degrades the heat dissipation, thus affecting the operating conditions of the cell-packs. Therefore, their usage without the so-called BMS is not recommended, as shown in the authors’ preliminary research. In practice, various BMS are used, most often with the so-called passive balancing. However, their application in mines is uncertain, due to the effect of heating under operation. When it comes to active BMS, they usually possess a quite complex structure and hence, are relatively expensive. Therefore, the authors conducted research for two specially developed active and one commercial passive BMS cooperating with selected lithium-iron-phosphate (LiFePO4) batteries when used in a suspended mining vehicle type PCA-1. The tests were carried out under environmental temperatures ranging from +5 °C to +60 °C. The effect of mismatching (12.5% to 37.5% of total cells number) of the cell parameters on the temperature distribution and voltage fading at the terminals of individual cells was checked. As a result of the investigations, the practical usefulness of the developed active BMS was determined, enabling the extension of the lithium-iron-phosphate battery life under onerous mine conditions, for a single recharge, which is a novelty. On the basis of the obtained results, appropriate practical conclusions were formulated.