Week 7 State of charge estimation

https://in.mathworks.com/matlabcentral/fileexchange/72865-design-and-test-lithium-ion-battery-management-algorithms

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

2.What is coulomb counting? Refer to the above model and explain how BMS implements coulomb counting for SOC estimation

Q1)

Ans:

Here we are using the default model with the default parameters:

The model is as follows.

• The above model is the battery harness dashboard .In this dashborad all the important indicators related to the faulty are displayed.Whne there is a fault in the battery then this dashboard can display which part of the battery is faulty.
• this will help in identifing the fault and automatic disconection can prevent for a hazard.
• In this model we are considering 3 test conditions .
• And we can change the test condtion by using the test sequence varrient block.
• test Sequence Variant block which allows you to select which test needs to be simulated.

Lets carry out the 3 test:

Test no.1

Here the simulation time for the model is 20000 sec (Default)

For the dashborad we can see there are all the green ligts no red light is dispayed that means there are no falut condition in this model.

%

• From the result plot we can see 1st vehicle is initially in the driving state and soc was 80 % .
• battery is discahrged till 46% after that the vehicle is at stand still then the vehicle is been connected for charging.Initially the charging time very fast til it reaches to 80-85% because of the constant current charging after that the volatge charging is is kicked in so the charging time to complete chrge the battery is increased.From the Cell temperatures plot it is observed that the battery temperature rises in driving and charging. The battery voltage was increased to 4.2 V while charging.
• The current plot shows the current value supplied to the vehicle while driving. The SOC was observed to be decreased around 50% in driving condition, which increased while charging.

Test No.2-

There are no faults detected in the model all the dashborad lights are green.

simulation time is same as test no 1

• From the plot we can see the vehicle is in the driving condition.At the starting the SOC was 80% .
• From the plot we can see test 2 does not inculde chraginf condition.
• The temperature of the cell is constantly risiing due to the internal resistance .The gap between the cell temperature is 300-320,the temperature gap should not be higher as this may result into decay of one cell faster then the other cell.
• The final SOC of the battery reaches less than 40%.

Test no-3

There is no fault, all the dashborad parameteres are showing dreen lights.

simulation is same as for test 1 and test 2.

• From the above plot we can see the BMS is showinf only charging condtion,at initial the battery is 80% charged,and the charger is pugged in,So now the battery slowely charging from 80 to 100%.
• Due to volatge charging the speed of the chraging is slow.
• The peak current settel down to zero.The cell balancing is done compleletly.
• And the cell temperature is also less as compared to the previous tests.Due to the slow charging the cell will generte less heat and the helt of the cell with los tempwerature can be maintained for longer duartaion of time.

2.What is coulomb counting? Refer to the above model and explain how BMS implements coulomb counting for SOC estimation

Ans:- The coulomb counting is a method to measure the SOC of the battery by measuring 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:

SOC(t)=SOC(t-1)+I(t)/Qn*T

Now how this coulombs counting methoed is used in the above model:-

To find coulomb counting in the model we go inside the BMS ECU block

Go to SOC estimation block,as we know the columb coutning is used to estimate the SOC .

By going through we can fing the coulomb counting at the top block

• This system carries out the estimation by coulomb counting equation:-SOC(t)=SOC(t-1)+I(t)/Qn*T
• The coulomb coutning method is more prefered because of the advantages,which is simple and the cost is also less.
• Temperature and current are taken as input from the battery.
• Current signal is given to the gain block and the temperature is given to capacity as it varies according to the temperature. These inputs are given to integration where current will be integrated wrt time. This output is given to another block where it is divided by capacity and in this way the SOC is estimated.

Conclusion:-

Thus we have tested all the three test conditions all observed the results and also studied about the coulobs counting.