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.
Answer:
Given Data
Rated Voltage rating: 120v
maximum voltage rating: 120v
minimum voltage rating: 100v
Rated power rating: 150Kw
continuous current requirement: Pmax = 1max* Vmax
Imax = Pmax/Vmax
Imax = 150*1000/120 =1250A
Peak current requirement: I/0.637 =1250/0.637 = 1962A
Peak current duration: 12min
Cell Comparison
Cell A (Cylindrical) Cell B (prismatic)
Nominal capacity:3.5Ah Nominal capacity: 4.5Ah
Max Current: 5A Max Current : 6A
Cell nominal voltage: 3.6V Cell Nominal Voltage : 3.6V
Max cell Voltage: 4.2V max cell Voltage : 4.2V
|
Cell A |
Cell B |
|
|
Maximum Discharge Current |
5A |
6A |
|
Temp (deg c) |
44 |
43 |
|
Time (min) |
15 |
15 |
Number of cells in series
Number of cells in series = Rated motor voltage / Nominal cell voltage
= 120/3.6 = 33.33
Rounding off the number of cells in series
Rounding off the number of cells depends on the maximum voltage and minimum voltage
case 1
Rounding off 33.33 to 33
Nominal battery voltage = Cell nominal voltage *33
= 3.6*33=118.8
Maximum battery voltage = cell maximum voltage *33
= 4.2* 33 =138.6V
Mini battery voltage = Cell minimum voltage *33
= 2.7*33 = 89.1V
case 2
Rounding off 33.33 to 34
Nominal battery voltage = Cell nominal voltage *34
= 3.6*34=122.4V
Maximum battery voltage = cell maximum voltage *34
= 4.2* 34 =142.8V
Mini battery voltage = Cell minimum voltage *34
= 2.7*34 = 91.8V
|
Battery voltage |
Case 1 |
Case 2 |
Targeted Voltage |
Values |
|
|
Battery Nominal voltage |
118.8 |
122.4 |
Nominal Voltage |
120V |
ok |
|
Battery Max Voltage |
138.6 |
142.8 |
Max Voltage |
120V |
|
|
Battery Min Voltage |
89.1 |
91.8 |
Min Voltage |
100V |
It's always better to have an EV Voltage
So, we can pick case 1 which is 34 cells in series
Number of cells in parallel 358
Cell A = 3.5Ah
Number of cells in parallel = continuous current/cell nominal capacity
= 1250/3.5 = 357.14
Cell B = 4.5Ah
Number of cells in parallel = iPhone continuous current/cell nominal capacity
= 1250/4.5 = 277.77
Rounding of the number of cells in parallel
Cell A = 3.5Ah
Number of the cells in parallel = 357.14
case 1
Battery capacity = 357*3.5 = 1249.5Ah
case 2
Battery capacity = 358*3.5 =1253Ah
Cell B = 4.5Ah
Number of the cells in parallel = 277.77
case 1
Battery capacity = 277*4.5 = 1246.5Ah
case 2
Battery capacity = 278*4.5 =1251Ah
it's always recommended to discharge the battery for continuous current in 1c.
Continuous current requirement = 1250A
So, we will Choose case 2 From both cellA and cell B
Cell peak Current
Individual cell peak current = Load peak current / Number of cells in parallel
Cell A = 3.5Ah
Number of cells in parallel 358
Individual cell peak current = 1962/358 = 5.48 A
Cell B = 4.5Ah
Number of cells in parallel 278
Individual cell peak current = 1962/278 = 7.05 A
|
Cell A |
Cell B |
|
|
Individual cell peak current requirement |
5.48A |
7.05A |
|
Maximum Discharge Current |
5A |
6A |
|
Temp (deg c) |
44 |
43 |
|
Time (min) |
15 |
15 |
So, cell A will be finalized and the number of cells in parallel will be 358
Battery pack configuration
--->> 33S358P is our battery pack configuration
b. Draw the BMS topology for this battery pack.
2)Build a 3S2P battery pack configuration with generic battery block using Matlab/Simulink.
Aim)The main aim is design a given battery pack configuration by using the Matlab/Simulink Tool.
Given data :-
Battery pack configuration = 3S2P
Simulink model :-
Batteries in 3S2P configuration in Matlab/Simulink. That is 3 cells should be connected in series and 2 cells should be connected in parallel.
Therefore,
Total number of cells in battery pack = No. of cells in series * No. of cells in parallel
Then ,
Total number of cells in battery pack = No. of cells in series * No. of cells in parallel
= 3 * 2 = 6 cells
Step-1
Arrangement of 6 cells:-
The figure 1 shows the arrangement of 6 cells.
We have to place total number of cells in battery pack (6 cells)
Arrangement of 6 cells
Parallel connection: -
The figure 2 shows the batteries connected in parallel.
For parallel connection, batteries are connected from terminals to same terminals of other batteries that is positive terminal (+) of one battery is connected with positive (+) terminal of other battery and negative terminal (-) of one battery with negative terminal (-) of other battery
Battery connected in parallel connection
Series and parallel conn
The figure 3 shows the battery connected in series and parallel combination. Batteries are connected from terminal to
terminal in a way that the positive (+) terminal of one battery is connected with the negative (-) terminal of the other
battery and negative terminal (-) of one battery is connected with the positive terminal (+) of the other battery.
Battery connected in series and parallel combination
Model Explanation:-
The voltage measurement block is connected across the battery pack to measure the battery pack voltage. The scope output used for the battery pack consists of SOC (State of Charge), Current and voltage. The controlled current signal is given as the load to the battery pack. The constant block is determined with battery capacity and it is given to the controlled current block.
The parameter given inside the battery is given below:-
- Nominal voltage of a cell 7.2V
- Rated capacity of a cell 5.4Ah
- Maximum voltage of a cell 8.3V
Therefore ,
Nominal voltage of the battery pack = no.of cell in series * nominal voltage of a cell
= 3 * 7.2v
= 21.6 V
Rated capacity of the battery pack = no.of cell in parallel* rated capacity of a cell
= 2 * 5.4Ah
= 10.8Ah
The model is for an 21.6V 7 with 10.8Ah battery capacity
Overall voltage of the battery pack = maximum voltage of the battery * no. of cells in series
= 8.3V * 3
= 25 v
Overall voltage = 25 V
Total Battery pack model:-
Output Scope results :-
Voltage scope :-
Overall voltage of the battery pack = maximum voltage of the battery * no. of cells in series
= 8.3V * 3 = 25 V
>>From the Above Plot is we can observe that the the total battery pack voltage is reduced bt 10% of the initial value.
Battery pack details:-
>> From the Above graph we can observe that the
Top Plot is (Voltage):-
>>The voltage is around 8.3V. The increasing and decreasing voltage is with respect to the regenerative braking
Middle Plot (Current):-
>> The current signal is determined by the load current is due to regenerative braking.
Bottom Plot(SOC%):-
>>The SOC (state of charge) is started to reduce from 100% to 99 % corresponding to the load given
Conclusion :-
The battery pack configuration(3S2P) with generic battery block using Matlab/Simulink is created.