4. Use Case

As a first step to designing a BMS, it is necessary to define a use case. While it sounds like an attractive goal to design a general-purpose BMS for each and every application, this is not possible as each implementation has to be adapted to its targeted application.

A simple example is that depending on the application, cells with high power or cells with high energy will be used. These cells will have different chemistries and behave differently.

Another example is a stationary battery storage used for peak shaving compared to the BMS used to monitor the cells in a vehicle: in the first case, it is easily possible to disconnect the battery in the case that a malfunction is detected. In the second case, this will probably not be possible: if the vehicle is driving at higher speeds in the traffic on a highway, it is not possible to simply disconnect the battery in the case that a malfunction is detected, because this would put the passengers in danger if the vehicle stops in the middle of the high speed traffic.

In this documentation and in the application implemented by default in the code, a stationary storage is considered. In case of error, the contactors will open and disconnect the battery.

Three power contactors are used to connect and disconnect the battery modules from the load:

  • Main Contactor Plus

  • Main Contactor Minus

  • Pre-charge contactor

There is no separate charge path, discharging and charging are made through the main contactors.

4.1. Example

An example a battery system is shown in Fig. 4.1.

Example of a battery system

Fig. 4.1 Example of a battery system