Week 7 State of charge estimation

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

Block simulation of harness test which is having BMS ECU and plant

Its harness Test dashboard which is having Test sequence varience , manual variant 9 lamp and BMS test sequance

Here we are selected variant 01 and run the simulation for 20000 sec

All the lamps run on and shows Green signal that mean No error in the program

So below Image shows the result we can observed that voltage rise upto 4.2 volt while charging and reduce upto 3.18 volt

Cell temperature also increase upto 317 in driving as well charging condition

At driving condition the SOC degreases and it will also increase while charging the battery

Below Image shows the zoom portion

Test sequence variant 2

Here we select the Sequence variant is 2

Here also lamp shows green signal that mean No error

Below result we can observed that battery is completely discharge at 8700 sec so vehicle stop at nearly 8700 second not move upto as like variant 1

But it reach upto maximum 3.9 volt and reduce upto 3.2 volt of battery cell

Maximum temperature is 323 k

Its zoom view of variant 2 result

Here we select the test sequence 3

And while running lamp shows green signal

Vehicle is continuously charge upto 0 to 20000 sec so SOC is constant

Voltage increases upto 4.21 v with increasing temperature upto 292.6 k

Below image is zoom view of above result

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

The coulomb method is used to measure discharge current of the battery and integrate the discharging current over the time in order to estimate SOC

SOC(t)=SOC(t-1)+Ic(t)/Qn.Δt

But above equation is just plain equation in practical several factor are affect on equation that is

Temperature , battery condition discharge current and life cycle of the battery

For increasing accuracy of the coulomb formula we consider all above factor and modify the current factor as

I_c(t)= k₂I(t)²+k₁I(t)+k₀

Where k₁ and k₂ and k₀ are the constant

So modify formula of coulomb counting is

SOC(t)=SOC(t-1)+Ic(t)/Qn.Δt

And BMS ECU IS

Now we see SOC block

Here on top we can clearly observed coulomb counting block

ADVANTAGE

We can see the result on lower computation cost

INPUT

Here we use Temperature and current as input but we integrate the current with respect to Time

OUTPUT

Output is given to discrete time integrator to track the safe chargeable time and then SOC estimate

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