As a central element in the battery pack, the battery management system (BMS) not only monitors and regulates voltage, current and temperature, but also ensures optimum interaction between the cells. The BMS is more than just a protective circuit for the battery pack. It can also take over central functions of the end application. The safety functions of the BMS are divided into 1st level protection and 2nd level protection.
The 1st level protection is a recoverable (reversible) protective device. It monitors the voltages of the individual cells and the battery pack, the charging and discharging current and the temperature. If one of the parameters is outside the limit values, the BMS prevents further charging or discharging.
In contrast to 1st level protection, 2nd level protection is irreversible: once triggered, the battery pack can no longer be used by the customer. An example of 2nd level protection is a fuse.
A battery pack is a rechargeable battery consisting of cells connected in parallel and/or in series in combination with a battery management system. The cells and the battery management system, including all connections, are combined in a battery housing, which in the simplest case can be a shrink tube, but usually consists of a solid plastic housing.