Project 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

Cell Specifications: 

Nominal Voltage= 3.6V

Max. Voltage= 4.2V

Nominal cell capacity= 3500mAh = 3.5 Ah

Rated power=150kw

Rated voltage=120v

First finding the motor current= (rated power *1000)/rated voltage

                                                = (150*1000)/120

                                                =1250A

 

Number of cells in series = total voltage /cell nominal voltage

Assuming the max voltage as the total voltage

Number of cells in series = 120 /3.6

Number of cells in series = 33.33

 

Rounding off the number of cells in series depends on

• Maximum voltage
• Minimum voltage

Test-1

 Rounding off 33.33 to 33

Nominal battery voltage = cell nominal voltage * 33

                                   = 3.6 * 33 = 118.8V

Maximum battery voltage = cell max voltage * 1

                                      = 4.2*33 = 138.6 v

Minimum battery voltage = cell minimum voltage * 1

                                      = 2.7 *33 =89.1V

 Test-2

 Rounding off 33.33 to 34

Nominal battery voltage = cell nominal voltage * 34

                                    = 3.6 * 34 = 122.4V

Maximum battery voltage = cell max voltage * 2

                                      = 4.2*34 = 142.8v

Minimum battery voltage = cell minimum voltage * 2

                                      = 2.7 *34=91.8V

 

Number of cells in parallel = Total current/cell nominal capacity

Number of cells in parallel = 1250/3.5

Number of cells in parallel = 357.14

 

The number of cells in series is taken as test-2 with 34 cells in series.

The number of cells in parallel is taken as 357 cells.

 

 The nominal voltage of the battery pack = no. of cells in series * nominal voltage of a cell

                                                            = 34* 3.6

                                                            = 122.4 V

Rated capacity of the battery pack = no of cells in parallel * rated capacity of a cell

                                                  = 357 * 3.5

                                                  = 1249.5Ah

The overall voltage of the battery pack = maximum voltage of a cell * no of cells in series.

The overall voltage of the battery pack = 4.2 * 34 = 142.8V

The battery pack configuration is 34s357p

The 34 cells are connected in series like shown below

b.Draw the BMS topology for this battery pack.

For the above battery pack we have to draw the BMS topology based on number of cells connected in series so the number of cells is 34 cells so the cells are more than 18 then we use master & slave topology

In this topology we using daisy chain interface means it collects the all data of slave-1 is sent to slave-2 collects the 17 cells data and the slave-2 and slave-1 data sent to micro controller unit. The topology is shown below

2.Build a 3S2P battery pack configuration with generic battery block using Matlab/Simulink. 

Total number of cells in battery pack = no.of cells in series * no.of cells in parallel

                                                            = 3*2

                                                            =6 cells

Series connection of a battery:

Batteries are connected from teminal to terminal in a way that the +ve terminal one battery is connected to -ve termnal of the other battery and -ve terminal of one battery is connected to +ve terminal of other battery.

Parallel connection of a batteery:

Batteries are connected from terminals to same terminals of the other batteries that is +ve terminal of one battery is connected to +ve terminal of other battery and -ve terminal of one battery is connected to -ve terminal of other battery.

 

The battery pack model is shown below

2)Build a 3S2P battery pack configuration with generic battery block using Matlab/Simulink. 

Aim)The main aim is design a given battery pack configaration by using theMatlab/Simulink Tool.

Given data :-

Battery pack configartion = 3S2P

Simulink model :-

For creating the Simulink model battery pack configartion we are used following blocks:-

Battery :-

scope:-

 

 

Procedure :-

 

Batteries in 3S2P configuration in Matlab/Simulink. That is 3 cells should be connected in series and 2 cells should be connected in parallel.

Therefor,

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

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) 

                   

                                                Figure 1: 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 ofother battery and negative terminal (-) of one battery with negative terminal (-) of other battery

 

                         

                                          Figure 2 : Battery connected in parallel connection

 

 

Series and parallel connection:-

          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.

                                  

 

                                           Figure 3 : 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 blockis 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

 

There fore ,

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 and the decrease in 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.