Project 1
Q.1.Design a battery pack for a car roughly 150 Kw with 120 V. Use a 3500 mAh 3.6V nominal NMC chemistry cell.
a. Design the battery pack configuration.
b. Draw the BMS topology for this battery pack.
ANS: Aim: The project aims to design the battery pack configuration, Draw the BMS topology for this battery pack using the given data, and also build a 3S2P battery pack configuration by using the MATLAB/Simulink tool.
Theory:
Battery Management System: A battery management system(BMS) is said to be the brain of the 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 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, and 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.
Solution: -
Given Data
Rated Voltage rating:120v
maximum voltage rating:120v
Rated power rating:150Kw
Battery capacity 3500 mAh= 3.5 Ah
Nominal voltage= 3.6 volts.
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 a series
case 1
Rounding off 33.33 to 33
Nominal battery voltage = Cell nominal voltage *33
= 3.6*33
=118.8 volts
case 2
Rounding off 33.33 to 34
Nominal battery voltage = Cell nominal voltage *34
= 3.6*34
=122.4 volts
It's always better to have an EV Voltage
So, we can pick case 2 which is 34 cells in series.
Number of cells in parallel:
Number of cells in parallel = Battery capacity / cell capacity
= 150*10^3 /120 / 3.6
= 1250 / 3.6
= 347.222222
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
= 34*347.222222
Total number of cells in battery pack=11805.5555
Battery pack configuration:
34S347P is our battery pack configuration
Now the battery pack is made of a 34S347P pack so that it can meet the required output of 120V, 150Kw.
b. Draw the BMS topology for this battery pack.
BMS topology is classified into the following four(4) types:-
1)Centralised Topology:
This Topology is used for only a pack of 18 cells or less than 18 cells in a series only.
2)Master and Slave topology:-
This Topology is used for a pack of 18 cells or greater than 18 cells in a series. High Energy storage purpose.
3)Modular Topology:
This Topology is used for pack of 18 cells or greater than 18 cells in a series. Large Energy storage purpose.
4)Distributed Topology:-
This Topology is used for pack of 18 cells or greater than 18 cells in a series. Very large Energy storage purpose
Solution:-
From the Architecture of BMS, we can say that the "AFU" Allows only 18 cells connected in series per one unit of module.
Hence,
we required a series cells is 34 cells
Therefore we are dividing these 34 cells as 2 slave sets with 1 number of MCU master units as follows
Slave 1= 17 cells
Slave 2= 17 cells
Based on these cells connected in series and Architecture of BMS we Choose the Master and Slave topology of BMS for this Ev battery pack Topology design.
Battery Management System (BMS):
BMS Topology used in this battery pack is Master and Slave BMS Topology. Because the total battery pack is made of sub-battery packs controlling and manufacturing will be easy.
Conclusion:-
We can conclude from the above calculations
*The battery Pack configuration is 34S347P.
*Battery BMS Topology is "Master and Slave " Topology is designed and explained theory regarding BMS topology.
Q.2. Build a 3S2P battery pack configuration with generic battery block using Matlab/Simulink.
ANS: The main aim is to design a given battery pack configuration by using the Matlab/Simulink Tool.
Given data:-
Battery pack configuration = 3S2P
Simulink model:-
For creating the Simulink model battery pack configuration we used the following blocks:
Battery
scope
Voltage measurement
Controlled current source
Bus selector
Powergui.
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.
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
Arrangement of 6 cells:-
Figure 1 shows the arrangement of 6 cells.
We have to place the total number of cells in the battery pack (6 cells)
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 by battery capacity and it is given to the controlled current block.
The parameter inside the battery is given below:-
Nominal voltage of a cell 3.6 V
The rated capacity of a cell is 3.5 Ah
Therefore,
Nominal voltage of the battery pack = no.of cell in series * nominal voltage of a cell
= 3 * 3.6 v
= 10.8 V
Rated capacity of the battery pack = no.of cells in parallel* rated capacity of a cell
= 2 * 3.5 Ah
= 7 Ah
Output Scope results:-
Voltage scope:-
Battery pack details:-
Conclusion:-
The battery pack configuration(3S2P) with a generic battery block using Matlab/Simulink is created.