Battery Management System and its Applications

11 Balancing/Balancing Control

11.1 Balancing Control Management and Its Significance

11.1.1 Two Expressions of Battery Capacity and SoC Inconsistency

As discussed in Chapter 9, the battery level is conceptually different from the SoC. Therefore, the battery inconsistency can be described in two different expressions.

The balancing control model discussed in this chapter is applicable to the battery pack with series structure. Supposing the number of the cells in the battery pack is n, and the following two expressions are given.

Expression by battery capacity combined with battery level

For the k cell shown in Figure 11.1, the maximum capacity of the battery is expressed as C_k (Ah) and the current battery level of the cell is expressed as R_k (Ah). The battery level of all cells is respectively expressed by R₁, R₂, …, and R_n, and the capacity of all cells is expressed by C₁, C₂, …, and C_n. The above model can be represented graphically, as shown in the Figure 11.2.

Figure 11.1 Battery pack formed by series connection of n cells.

Figure 11.2 Expression by battery capacity combined with battery level.

It can be seen in Figure 11.2 that the columns have the same width and their height represents the battery capacity C₁, C₂, …, and C_n . The dark color parts represent the current ...