Week 7 State of charge estimation

Question 1: Simulate the 3 test cases from harness dashboard and write a detailed report on the results.

Solution 1:

Test Sequence 1 Result:

In test sequence 1 there are different states:

1. Driving: During time period of 0 to 3000 sec driving condition is selected which means battery is been discharge. As a result the SOC of battery reduces from 80% to 45% approx. Battery voltage and current both reduces to some limits. On completing 3000 sec the state changes to Balancing
2. Balancing: As soon as 3000 sec completes the balancing of battery pack is done. This result in constant cell voltage, current, and SOC gets constant of time period.
3. Charging and Balancing: Next step is charging condition battery states shifts to charging after 4000 sec and this result in increase cell voltage, cell current, and increase SOC.
4. Post Charge Balancing: Post charging state of battery starts from 9000 sec and cell voltage increase to 4.2V current becomes 0 and SOC gets constant.

Test Sequence 2 Result:

In test sequence 2 there are different states:

1. Driving: During time period of driving condition is selected which means battery is been discharge. As a result the SOC of battery reduces from 80% to 0% approx. Battery voltage and current both reduces.

Test Sequence 3 Result:

Test sequence 3 there are different states:

Charging condition of battery increase cell voltage and increase SOC of battery pack.

Solution 2: Coulomb Counting may be defined as integration of current over the period of time along with temp in consideration.

The figure shows the BMS implementation of coulomb counting for SOC estimation. A peak current is multiplied by constant value of (1/3600) and look up table of temperature is created which is divided to obtain the result. The result is further integrated using discrete time integrator block to get coulomb counting for SOC estimation.