Week 7 State of charge estimation

Problem Statement - What is coulomb counting? How BMS implements coulomb counting for SOC estimation?

The Coulomb counting method measures the discharging current of a battery and integrates the discharging current over time in order to estimate SOC. Coulomb counting method is done to estimate the SOC(t), which is estimated from the discharging current, I(t) , and previously estimated SOC values,SOC(t-1) . SOC is calculated by the following equation:

From the monitoring system the BMS receives the overall pack current after considering current data from all parallel battery stacks. This pack current is converted to amp-hour rating(1/3600 gain block) and divided by the maximum capacity possible at a given temperature(a look up table is used for this purpose). The number so produced, is than integrated with respect to time(using the discrete time integrator block that has the initial condition), which yields the value of SOC.