1.2.1 Passive BMSs-switched shunting resistor balancing Shunting resistor passive BMSs are the most straightforward cells SOC balance concept. They are based on removing the excess energy from the higher voltage cell(s) by bypassing the current of the highest SOC cell(s) and wait to until the lower SOC cell(s) to be in the same level. The shunting resistor methods can be categorized into two methods as shown in Fig. 2. The first method is fixed shunt resistor (FR), is shown in Fig. 2-a. The second method is controlled shunting resistor or switched shunt resistor (SR), is shown in Fig. 2-b. The two methods can be used for the low power applications with drawing current smaller than 10mA/Ah as recommended in [4r] to limit the energy dissipated into the shunt resistors. 1.2.1.1 Fixed shunt resistor …show more content…
2-a. The current drawn by each shunt resistor is linearly proportional to the cell voltage. As the cell voltage increases, more current is drawn by the shunt resistor. This will decrease the voltage differences between the different cells within the battery system since higher voltage cells is further discharged by the shunt resistors. It is worth mentioning that this method can be only used for Lead-acid and Nickel based batteries because they can be brought into overcharge conditions without cell damage [4r]. Its features are simplicity, low cost but the excess energy is converted into heat losses in the shunt resistors. In addition, the current drawn by the shunt resistors is not regulated. As a result, the cell voltages are not fully regulated