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.
a. Design the battery pack configuration.
b. Draw the BMS topology for this battery pack.
Solution:
We have a battery pack of 150 Kw with 120 V. Use 3500 mAh 3.6V nominal NMC chemistry cell.
Battery pack is the combination of cells in series and parallel.
To calculate the cells in series we have a formula= Max cell voltage/Nominal cell voltage.
=(120)/(3.6)
=33.34 rounding off to 34
We require 34 cells in series.
To calculate the cells in parallel we have a formula= Max battery pack current/cell current
Max battery pack current is unknown, to calculate we have
Power=I*V
150kW=I*120V
I=(150K/120)=1250A
No of cells in parallel=(1250A/3.5A)=357.14 cells rounding off to 358 cells in parallel.
So the battery pack configuaration now consist of 34S 358P.
For designing the battery back topology of "Master & Slaves" we consider only series cells.
In each module max 18 cells are occupied. There are 34 cells totally. so I have connected 17 cells in 1st slave and another 17cells group in 2nd slave.
2) Build a 3S2P battery pack configuration with generic battery block using Matlab/Simulink.
Solution: A battery pack module with 3S2P configuaration using simulink.
Total no of battery cells used are the product of no of cells in series & no of cells in parallel.
ie 3*2=6 no of cells.
3 cells are connected in series shown column wise. 2 cells are in parallel shown row wise.
The blocks used for building simulink model are
1) Battery block
2) Controlled current source block
3)Constant input block
4) Voltage measurement block
5)Display block
6) Scope block
7) Power Gui
Simulink model for 3S2P battery configuaration
Here the Battery input voltage given is 4.2V and the output is observed in display block is 25V
Individual battery cell nominal voltage is:7.2V
Rated capacity(Ah):5.4Ah
Initial SOC=100%
Max charge voltage=8.3807 V In display block 8.3807*3=25V ie displayed in display block.
Nominal voltage of the battery pack= Nominal voltage of the cell*no of cells in series.
Vnom=7.2*3=21.6V
Rated capacity of the battery pack=No of cells in parallel* rated capacity of the cell
=2*5.4Ah=10.8Ah
So the battery pack model has 21.6V,10.8Ah battery capacity.
Discharge of each battery cell as shown below.
The output SOC , Voltage and current graphs are shown below.
The simulink file is attched for reference.