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.
ANS =
Let us concider the cells with
Nominal voltage = 3.6v
Capacity = 3500mAh = 3.5Ah
To meet the requirment of 120v and 150Kw, we need to find the number of cells connected in series and parallel.
First convert the battery capacity 150Kw to Ah
Amper hour = Watt hour / Voltage
Amper hour = 150*1000 / 120 = 1,250 Ah
series:
no. of cells in series = total battery voltage / nominal voltage of the cell
no. of cells in series = 120 / 3.6
no. of cells in series = 33.33
We have to round off to lower value and higher value
Case-1) Number of cells in series = 33
Case-2) Number of cells in series = 34
Total volatge = nominal votage of cell * number of cells in series
| Number of cells in series | total voltage | Requred voltage | |
| Case - 1 | 33 | 33*3.6 = 118.8 | 120 |
| Case - 2 | 34 | 34*3.6 = 122.4 | 120 |
The condition to choose the number of cells are
Nomial voltage of battery should not excide the Load volatge
Max Volatge of battery should be less than the Load Max Volatge
Min Volatge of battery should be greater than the Load min Voltage
We have to round off to lower value so that it will not excide the required value
Therefore Number of cells in series = 33
Output total volatge will be 118.8V
The output voltage can be adjusted to 120v by a Buckboost converter to meet the requirment of 120v
parallel:
no. of cells in parallel = required capacity / cell capacity
no. of cells in parallel = 1250 / 3.5
no. of cells in parallel = 357.14
We have to round off to lower value and higher value
Case-1) Round off to lower value = Number of cells in series = 357
Case-2) Round off to higher value Number of cells in series = 358
The output capacity = cell capacity * number of cells in parallel
| Number of cells in Parallel | total Capacity(Ah) | Requred voltage | |
| Case - 1 | 357 | 357*3.5 = 1,249 | 1250 |
| Case - 2 | 358 | 358*3.5 = 1,253 | 1250 |
We can round off to higher value = 358
The output capacity = each cell capacity * number of cells in parallel = 358*3.5 = 1,253Ah
The number of cells in Parallel = 358
The Output Capacity will be 1,253Ah
The Current can be limitted to requied value bu using current limitters.
total no. of cell = 358* 34 = 12172
Now the battery pack is made of 33S358P pack so that it can meet the required output of 120v,1250Ah or 120V 150Kw
b. Draw the BMS topology for this battery pack.
for 33S358P we choose the master & slave topology beacuse the modular topology is for MAh rating.
for the BMS topology only series cell are consider.
so, there are 33 cell in series
so, we distribute the 17 cell in one slave & 16 cell in another slave .
1st slave of AFE give the data to the salve2 of AFE.
both the data is given to MCU (Master) by using 2nd slave.
2) Build a 3S2P battery pack configuration with generic battery block using Matlab/Simulink.
ans =
for the 3S2P BATTERY PACK CONFIGURATION WE USE FOLLOWING BLOCK:
1) battery
2) resistance
3) bus selector
4) scope
5) powergui
simulink model :
output :
explanation:
in a simulink model we use the 3 cell in series & 2 cell in parallel & this connected to the load . measurement terminal of battery is connected to scope by using bus selector.
so, we got the soc ,current & voltage in output.
conclusion :
from the above experiment we learn how to configure the battery pack configuration & according to that draw the BMS topology & also drawning the battery pack configuration in simulink & according to that output will be obtained.