Battery management includes the monitoring, control, and protection of batteries, making it an essential part of any battery system. Battery management must meet different complex requirements based on the storage application and cell chemistry. Thus, the number of tasks to be monitored and parameters to be regulated is many times greater for a traction battery in an electric vehicle than for a mobile phone battery.
Exceeding the maximum permissible current or cell voltage limits can lead to cell damage or even failure. As such, single cell monitoring of the electrical variables as well as limiting the battery current are among the core tasks of battery management.
Temperatures which are either too high or too low have a negative impact on the life of the cell and can in extreme cases result in internal short circuits or a thermal runaway. Temperature monitoring of the battery system, the modules or even the individual cells by the battery management system is therefore necessary. For passive systems, the battery current is limited to a greater extent if necessary. The temperature can be controlled directly using active air conditioning.
The battery management system is also responsible for balancing cells with different states of charge within a series connection
as well as determining the state of the battery system. In particular, accurate state of charge (SOC) estimation, both for the individual cells of a pack and for the entire battery, is significant for the superordinate energy management and estimation of the remaining range or service life in mobile applications.
Important cell parameters, such as capacity and internal resistance, change over the life of a cell. Therefore, the value or state of health (SOH) of the parameters is continuously estimated based on the electrical measurements and stored models.
In order to avoid violating the operating limits, the charge acceptance (CA), the maximum possible performance (CC, cold cranking) as well as the energy reserves are calculated on the basis of measurements and the estimated states and cell parameters. This information (SOF, state of function) is communicated to the superordinate energy management.