Project - 1 Battery Pack Design

*** 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.

Aim of the Project:-

The Main Of this project is Design the battery pack configuration ,Draw the BMS topology for this battery pack using given data and also build 3s2p battary pack configaration by using the MATLAB/SIMULINK tool.

Theory:-

Battery Management Stysytem :-

A Bttery management system(BMS) is said to be the brain of a battery pack. The BMS is a set of electronics that monitors and manages all of the battery’s performance. Most importantly, it keeps the battery from operating outside of its safety margins.

The battery management system is critical to the battery’s safe operation, overall performance, and longevity of battery pack.

The primary function of the BMS is to protect the battery cells from damage caused by being overcharged or over-discharged. Additionally, the BMS calculates the remaining charge, monitors the battery’s temperature, monitors the battery’s health and safety by checking for loose connections and internal shorts.

The BMS also balances the charge across the cells to keep each cell functioning at maximum capacity.

Fig--> Battery management system

Solution :-

Given data:-

Required Power = 150 KW

Required Voltage = 120 V.

Battery detalis :-

Batatry capacity = 3500 mAh= 3.5 Ah

Battery Nominal Voltage =3.6V

a) Design the battery pack configuration.

for desiginig the Battery pack Configaration ,Firstly we have to fing the two parameters as followes :-

i) Number of cells connected in Series

ii) Number of cells connected in Parallel.

i) Number of cells connected in Series:-

For this solution let us Take the data from given:-.

Nominal volatge =3.6 v

Cell having capacity of cell(Ah)= 3500 mAh= 3.5 A

Formula :-


       Cells connected in series = Required voltage (V) /  Nominal cell Voltage(Ah)

From the data

Required Voltage :- 120 v

Nominal Voltage = 3.6 v

Therefore,

*** Cells connected in series = Required voltage (V) / Nominal cell Voltage(Ah) ***

The cells connected in series = 120 / 3.6

=33.3 cells

This Digits vallues are taken as rounding of caluctions as followes :-

Rounding of calculation:-

>>When compare with rated voltage, the battery voltage is greater in case 2 then case 1.

So,

No.of cell in series= 34 S

                Number Of Cells Connected IN Series = 34S  -------------(1)

ii) Number of cells connected in Parallel:-

Formula for number of cells connectd in parallel:-

Formula:-


Number of cells connected in Parallel = Required Contuinous Current(I) / Cell Nominal Voltage(V)

Given data:-

Required Power = 150 KW

Required Voltage = 120 V.

NMC Battery detalis :-

Batatry capacity = 3500 mAh= 3.5 Ah

Battery Nominal Voltage =3.6V

We know that ,

          Power(P) = Current(I) * Voltage(V)

             from above formula


     **** Current(I) = power(P) / Voltage(V) ****

hence, From formula,

Current(I) = power(P) / Voltage(V)

= (150 *1000) / 120

Current(I) = 1250 Amps

NMC Battery detalis :-

Batatry capacity = 3500 mAh= 3.5 Ah

Battery Nominal Voltage =3.6V

Therefore,

Number of cells Connected in paralle :-

Formula:-



  Number of cells Connected in paralle = Required Current (I) / Cell Nominal Voltage(V)

from the data ,

Current(I) = 1250 Amps

Cell nominal Voltage = 3.6 V

then ,

Number of cells Connected in paralle = Required Current (I) / Cell Nominal Voltage(V)

=1250 / 3.6

=358 P

There fore

           

                  Number of cells Connected in paralle =358 P--------------(2)

From values (1) and (2)

            Number Of Cells Connected IN Series = 34S

            Number of cells Connected in paralle =358 P

We can conclude that

The Battery pack Configaration = 34S358P

Battery pack Configaration image :-

Fig--> Battery Pack Configaration (34S358P)

b. Draw the BMS topology for this battery pack:-

BMS Topology:-

Fig :-BMS TOPOLOGY BLCOK DIAGRAM

Basically BMS topology is classified into following foure(4) types:-

1)Centralised Topology;-

This Topology is used for only pack of 18 cells or less than 18 cells in a series only.

2)Master and Slave topology:-

This Topology is used for pack of 18 cells or grater than 18 cells in a series .

High Energy storage purpose

3)Modular Topology :-

This Topology is used for pack of 18 cells or grater than 18 cells in a series .

Large Energy storage purpose

4)Distributed Topology:-

This Topology is used for pack of 18 cells or grater than 18 cells in a series .

Very large Large Energy storage purpose

Solution:-

From the Architecture of BMS we can said that the "AFU" Allowes ony 18 cells connected in series per one unit of modulae.

Hence ,

we required series cells is 34 cells

There fore we are dividing these 34 celss as 2 slave sets with 1 number of MCU master unit as followes

Slave 1= 17 cells

Slave 2= 17 cells

Based on this cells connected in series and Architecture of BMS we Choose the Master and Slave topology of BMS for this Ev battery pack Topology design.

BMS Topology MODEL :-

Master and Slave Topology:-

>> Above Model is For BMS Topology of 34s358P battery pack Configarationmodel

>>This Topology consistes a 2 numbers of slave of AFU units with each AFU units slave Consists a 17 numbers Of Cells connectd in series.

Conclusion :-

We can conclude from above calculations

The battery Pack configaration is 34S358P

Battry BMS Topology is "Master and Slave " Topology is is designed and explained thery regarding BMS topology.

--------------------------------------------------------------------------------------------------------------------------------------------

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
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)

Figure 1: Arrangement of 6 cells

Step@2)

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

Step@3)

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.

---------------------------------------------------------------------------------------------------------------------------------------------

(The End)