I have modelled a lithium ion cell in simulink using the 2RC equivalent circuit approach. I want to connect multiple cells in series and parallel to form a complete battery pack. In the literature I found this done in simscape but I want to implement it in simulink. The input to the cell is current and outputs are State of Charge and terminal voltage. Please advise me on how to connect multiple cells in series and parallel.
Dear Arpita,
welcome,
When you connect battery cells in series and in parallel, the cells must be theoretically identical. Practically there are some slight variations in their performance parameters due to fabrication tolerances.
When they connected in parallel they must have the same voltage.
When they connected in series they will have the same current.
So you build the battery pack according to the requirements of the load.
Assume that the voltage requires is VL,
then the number of cells that must be connected in series Ns>= VL/ Vcell,
where Vcell is the nominal cell voltage.
The number of cell strings to be connected in parallel Np >= IL/ Icell
where IL is the load current and Icell is the nominal cell current.
To get the equivalent circuit you substitute every cell be 2RC circuits.
I f the cells are identical, the summation of of the equivalent circuit will be staight forward. Ztotal= Ns Zcell/ Np= (Ns/Np) Zcell
where Z ell is = 2 RC circuits.
So, the equivalent impedance will be a scaled 2 RC circuits with the impedance scaling factor= Ns/Np.
This is a solution of your question.
Best wishes
Hi,
mathworks.com/matlabcentral/fileexchange/36019-battery-modeling
Also you can try the cell from Simulink library directly:
https://www.mathworks.com/help/physmod/sps/powersys/ref/battery.html
Hope this helps.
Dear Arpita,
welcome,
When you connect battery cells in series and in parallel, the cells must be theoretically identical. Practically there are some slight variations in their performance parameters due to fabrication tolerances.
When they connected in parallel they must have the same voltage.
When they connected in series they will have the same current.
So you build the battery pack according to the requirements of the load.
Assume that the voltage requires is VL,
then the number of cells that must be connected in series Ns>= VL/ Vcell,
where Vcell is the nominal cell voltage.
The number of cell strings to be connected in parallel Np >= IL/ Icell
where IL is the load current and Icell is the nominal cell current.
To get the equivalent circuit you substitute every cell be 2RC circuits.
I f the cells are identical, the summation of of the equivalent circuit will be staight forward. Ztotal= Ns Zcell/ Np= (Ns/Np) Zcell
where Z ell is = 2 RC circuits.
So, the equivalent impedance will be a scaled 2 RC circuits with the impedance scaling factor= Ns/Np.
This is a solution of your question.
Best wishes
Yes, you can do that in MATLAB using PCM based modules, and your results won't be accurate until you test each and every cell RC characteristics accurately. You also have to look into the hysteresis factors here. Else, the solutions can only be in ideal conditions. The experimentation with practical nature of batteries would help you understand the actual dynamics in the system.
Best wishes.
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