The term battery management system (BMS) refers to a structure that allows a battery pack to be kept in a safe operating area. A relatively advanced battery management system is expected to provide the following functions:

• keeping the battery pack between specific voltage values, preventing overcharging and discharging. It is particularly important in case of use of the Lithium-based batteries (LiPo, LiIon, LiFe);
• to keep the battery pack within certain temperature limits and to intervene in the system to provide these limits when necessary;
• measuring and limiting the charge and discharge current;
• reducing voltage imbalances between cells to increase the productive use capacity of the battery pack;
• remaining useful life (RUL), state of charge (SoC) and state of health (SoH) estimation.

The physical layer of a battery system includes the battery cells, the surrounding circuitry, and the connections with the BMS. The battery cells have certain limits (lower and upper voltage/current bounds) and demonstrate specific behaviour towards different power requests. The BMS and the circuity components are responsible for monitoring the battery cells and protecting them from overvoltage, under voltage, overcurrent, overloading, and also overheating.

The BMS can be any system that manages the battery. As discussed, batteries are sensitive to overcharging and deep discharging because they may damage the battery, therefore shortening its lifetime and even causing hazardous situations. This requires the adoption of a proper BMS to maintain the states of each cell of the battery within its safe and reliable operating range. In addition to its primary function of battery protection, a BMS should estimate the battery status to predict the actual amount of energy that can still be delivered to the load.