Project 1
Aim :- 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 :-
Given :-
Capcity of Battery Pack :- 150 Kw
= 150,000 W
Voltage ratting of battery pack :- 120 V
Nominal Voltage :- 3.6 V
Power of Battery pack :- 3500 mAh
=3.5 Ah
To Find :-
Number of cells connected in series
Number of cells connected in parallel
Solution :-
We know that to design any battery pack we need to know number of cells connected in seires & Parallel
Step :1- To calculate number of cells connected in series
No. of cells in series = Total Voltage / Nominal Voltage
= 120 / 3.6
= 33.34 `cong` 34 Nos.
Step :2 - To Calculate number of cells connected in parallel
No. cells in parallel = Total Current / Single Cell capacity
current of each cell = Power of battery pack / Total voltage
= 150,000 / 120
= 1250 Ampere
Now puting values in formula
No. cells in parallel = Current of each cell / Power of battery pack
= 1250 / 3.5
= 357.14 `cong` 358 Nos.
So , to Design a battery pack for a car roughly 150 Kw we need 34S358P ( 34 Cells connected in series & 358 cells connnected in parallel) Battery pack
b. Draw the BMS topology for this battery pack :-
To design an BMS for EV Battery 3.5 Ah , the best suitable BMS topology is "Master & Slave Topology"
Master & Salve Topology ,
- In this type of topology battery pack which consist of more than 18 cells in series.
- If we consider each cell of maximum volatge is 4.2 V & Nominal voltage of 3.6 V
- The Master & Slave topology more no of slave each slave consist of minimum 18 cells of Nominal voltage of 3.6 V.
So , for making battery pack of 220 V we have to take a 4 no of slave of
Slave No 1 : 12 Cells (each of 3.6 V)
Salve No 2 : 12 Cells (each of 3.6 V)
Salve No 3 : 10 Cells (each of 3.6 V)
Now addition of Slaves =
Slave No 1 + Slave No 2 + Salve No 3
= 12 + 12 + 10
= 34 Nos
BMS Topology Architechture :-
Aim : Build a 3S2P battery pack configuration with generic battery block using Matlab/Simulink :-
To Design a 3S2P battery pack :-
Step :1 Arrangement of 3S2P cells ,
Step:2 Series Connection ,
Fig shows the battery connected in Serieserminal of battery combination.Batteries are connected from terminal to terminal in a way that positive(+) terminal of one battery is connected with negetive (-) terminal of the battery and negetive (-) yerminal is connected with the positive terminal (+) of other battery.
Step 3 Parallel connection ,
The fig shows batteries connected in parallel. for parallel connection , batteris are connected from terminals to same terminal of other battery i.e. positive (+) terminal of battery is connectrd to positive (+) terminal of other battery & Negetive (-) terminal of battery is connectrd to negetive (-) terminal of other battery.
Step 4 Design of battery pack using simulink model ,
The parameter given inside the battery is given as ,
| Sr.No | Battery Parameters | Value |
| 1 | Nominal Voltage of cell | 3.6 V |
| 2 | Rated capacity of a cell | 3.5 Ah |
| 3 | Maximum voltage of a cell | 4.2 V |
Single battery output for SOC , Volatge & current ,
- Plot No 1: The SOC (state of charge) is started to reduce from 100% to 50% corresponding tothe load given.
- Plot No 2: The current signal is detrmined by the load and the decrease in current is due to regenerative braking.
- Plot No 3 : The voltage is around 8.3 V. The increasing & decreasing voltage is with respect to the regenerative braking
The overall output voltage of the battery pack is given as ,
Conclusion :-
- To Design a battery pack for a car roughly 150 Kw with 120 V. Use 3500 mAh 3.6V nominal NMC chemistry cell the reqiure cells which connected in series are 34 Nos. & cells connected in parallel are 358 Nos.
- In this case the best suitable BMS Topology is master & Slave Topology.
- Design of 3S2P (3 Cells are connected in series & 2 cells are connected in parallel) is studied by using simulink model & Understand the output with SOC % , Current & Voltage plot Also with overall output voltage of battery pack plot.