Project 2 Thermal modeling of battery pack
For a 10 cell series lithium ion battery model, simulate the thermal effects and compare life cycle performance at various temperatures, charge & discharge rates using MATLAB.
Here I took the power battery aging matlab example
Some modification done in the above example to get the required model
The function blocks used are :
- a set of 10 cells lithium ion battery connected in series
Subsystem of 10 cell series battery:
- cycle generator subsystem:
Matlab function block
function [ibatt,State] = fcn(SOC,SOCmin,Idis,Icharge,Stateprev)
%#codegen
State=Stateprev;
if(Stateprev==1 && SOC<=SOCmin)
State=0;
end
if(Stateprev==0 && SOC>=99)
State=1;
end
if (Stateprev==1)
ibatt=Idis;
else
ibatt=-Icharge;
end
- Controlled current source
- constants for providing charge current input and temperature input
- stair generator for charge current input
- Stair generator for DOD input
Simulink Model:
Simulation:
Case 1: Running the model at 25 deg celcius ambient temp and 20A charge current for 10 hours(36000 sec)
- At t = 0 s, the battery cycling starts with a discharge current of 20 A (0.5 C-rate), at ambient temperature of 25 degrees C. The initial SOC is 100 %. The discharge goes on until the SOC reaches 80 % (DOD of 20%). Afterwards, the battery is charged to 100 % SOC with a charge current of 20 A. As this cycle is repeated, the battery age increases whereas its capacity decreases. The internal cell temperature also increases from 25 degrees C to 31 degrees C.
- the cycle of soc% decreasing to 80% and increasing to 100% continues till end of simulation
- After each cycle of soc the age of battery increases slightly and reached 1.2 at the end of simulation
- total capacity of battery also keeps on decreasing
Case 2 Running the model at 40 deg celcius ambient temperature and 20 A current
- At t = 0 s, the battery cycling starts with a discharge current of 20 A (0.5 C-rate), at ambient temperature of 40 degrees C. The initial SOC is 100 %. The discharge goes on until the SOC reaches 80 % (DOD of 20%). Afterwards, the battery is charged to 100 % SOC with a charge current of 20 A. As this cycle is repeated, the battery age increases whereas its capacity decreases. The internal cell temperature also increases from 25 degrees C to 45 degrees C.
- the cycle of soc% decreasing to 80% and increasing to 100% continues till end of simulation
- After each cycle of soc the age of battery increases slightly and reached 1.6 at the end of simulation
- total capacity of battery also keeps on decreasing
Case 3 Running the model at 50 deg celcius ambient temperature and 20 A current
- At t = 0 s, the battery cycling starts with a discharge current of 20 A (0.5 C-rate), at ambient temperature of 50 degrees C. The initial SOC is 100 %. The discharge goes on until the SOC reaches 80 % (DOD of 20%). Afterwards, the battery is charged to 100 % SOC with a charge current of 20 A. As this cycle is repeated, the battery age increases whereas its capacity decreases. The internal cell temperature also increases from 25 degrees C to 55 degrees C.
- the cycle of soc% decreasing to 80% and increasing to 100% continues till end of simulation
- After each cycle of soc the age of battery increases slightly and reached almost 2 at the end of simulation
- total capacity of battery also keeps on decreasing
Conclusion:
As the ambient temperature of battery increases the aging of battery happens faster.