Week 7 State of charge estimation

Q1).Simulate the 3 test cases from harness dashboard and write a detailed report on the results?

Procedure-

1) Download the matlab model from the given link and open the matlab

2)Select the test sequence and run

Test 1)-

When simulation will start, the model will be in driving condition. After 3000 seconds it will be in standby mode and after 1000 seconds it will be in charging mode. Now by Running the simulation.

results

as we can see in the results

• the vehicle is initially in driving state
• as the SOC of battery goes down the vechile is now at charging till SOC gets to a higher point
• one of the cells has reached SOC to 1 before others

peak cell temp goes to 320k

Test 2-

now run the simulation by changing test sequence

Results-

From the above graph , a fault condition occured in second case. So the BMS is at driving state ever after all te cell have reached their cotoff voltage

Test 3-

Now by changing the test Sequence Value to 3

Result-

• Bms is in the charging state
• Temp of all cell is quite stable at 293k
• avg Soc is above 0.9

Q2)-What is coulomb counting? Refer to the above model and explain how BMS implements coulomb counting for SOC estimation ?

Ans 2)-coloumb counting method

The coulomb counting method is also known as the battery current integration method. In this method, a discharging/charging current I(t) is measured and integrated over time to calculate the amount of energy remaining inside the battery. In this method, SOC is taken at the previous time step SOC(t-1) and the amount of energy removed/added at the current time step is subtracted/added from the SOC of the previous time step SOC(t-1) to obtain the amount of energy present in the battery at the present instant.

The SOC estimation in the coulomb counting method is done using the below equation,

SOC(t)=SOC(t−1)⋅∫tt−1It⋅ηQn⋅dt