Project 1
Project 1 :
1. Design a battery pack for a car roughly 150 Kw with 120 V. Use 3500 mAh 3.6V nominal NMC chemistry cell.
Solution :
Part A - Battery pack configuration :-
Given Data,
Power = 150 Kw
Max. Voltage = 120 V
Battery Capacity = 3500 mAh
Nominal Voltage = 3.6 v
Now calculating no. of cells in series,
no. of cells in series = Rated voltgae /Nominal voltage of cell
= 120/3.6
no. of cells in series = 33.33 Nos
1) Rounding off above number to 33,
Nominal Battery voltage = 33 * 3.6
Nominal Battery voltage = 118.8 V
2) Rounding off above number to 34,
Nominal Battery voltage = 34 * 3.6
Nominal Battery voltage = 122.4 V
Here we will consider 34 cells in series as it matches the maximum voltage requirement and its always better to have more voltage than nominal.
As we know,
P = V * I
I = P / V
= 150 kW / 120
I = 1250 Amp
Next calculating no. of cells in series,
no. of cells in parallel = Total current / Cell nominal capacity
= 1250 A / 3.5 Ah
no. of cells in parallel = 357.14 Nos
1) Rounding off above number to 357,
Battery Capacity = 357 * 3.5 Ah
Battery Capacity = 1249.5 Ah
2) Rounding off above number to 358,
Battery Capacity = 358 * 3.5 Ah
Battery Capacity = 1253 Ah
In this case we will consider the number of parallel cells as 357 because its matching the total current requirement and not exceeding the value. So the final Battery pack 33S357P i.e 33 cells in series & 357 cells in parallel.
Part B - BMS topology for this battery pack :-
As the Battery pack configuration contains 33 cells in series and 357 parallel so topology must be consider which has capacity to handle more than 18 cells and high voltages. So in our case ' Master & Slave Topology' is selected as depicted in below fig.
2. Build a 3S2P battery pack configuration with generic battery block using Matlab/Simulink.
Solution :-
3S2P battery pack configuration with generic battery block using Matlab/Simulink :-
As the aim suggest the model configuration is 3S2P i.e 3 cells in series and 2 in parallel. So we have built a simulink model as shown in provided below figure, in this model we have chosen a standard cell data sheet which contains the all parameters related to the cell and battery pack. We have considered 'Panasonic CG 420A Pin type Li-ion battery' the data is provided below for this battery cell,
Data -
Calculations -
Total Number of cells in battery pack = no. of cells in series * no. of cells in parallel
Total Number of cells in battery pack = 3 * 2 = 6 nos
Actual parameters of Panasonic Cell,
1) Nominal voltage of cell = 3.8 V
2) Maximum voltage of cell = 4.35 V
3) Rated capacity = 22 mAh
Next,
Nominal voltage of battery pack = no. of cells in series * nominal voltage of cell
Nominal voltage of battery pack = 3 * 3.8 = 11.4 V
Rated Capacity of battery pack = no. of cells in parallel * rated capacity of cell
Rated Capacity of battery pack = 2 * 22 mAh = 44 mAh
Hence the below built model is for 11.4 V & 44 mAh
Simulink Model -
1st Scope Output -
2nd Scope Output -
Observation -
The 2nd scope output is the overall battery pack voltage and its calculation be made as follows ,
Overall battery pack voltage = maximum voltage of cell * no. of cells in series
Overall battery pack voltage = 4.4 * 3 = 13.2 V
Conclusion: As the theoretical values are successfully verified in the built simulink model so it can be concluded that the aim is successfully achived by developing the 3S2P battery pack configuration using MATLAB and Simulink.