Project 2 Thermal modeling of battery pack

AIM: Thermal Modeling of Battery Pack.

Objective:

• For a 10-cell series lithium-ion battery model, simulate the thermal effects and compare life cycle performance at various temperatures, charge & discharge rates using MATLAB.

The performance and life-cycle costs of electric vehicles (EV) and hybrid electric vehicles (HEV) depend on energy storage systems such as batteries. Thermal modeling of battery pack performance is crucial to optimizing these parameters. This part of the project will simulate the thermal effects on battery chemistry and compare life cycle performance at various temperatures, charge & discharge rates using MATLAB.

Temperature and temperature uniformity has a strong influence on battery performance. All the modules in the pack should be operated within the optimum temperature range suitable for the particular electrochemical couple used. In addition, the uneven temperature distribution in a pack leads to different charge/discharge behavior, resulting in unbalanced modules and reduced pack performance. Because high-energy-density batteries such as HEVs undergo aggressive charging/discharging profiles, thermal issues in an HEV pack are of more concern than in EV packs.

In the project, we will simulate the thermal effect of a 10S1P lithium-ion battery pack. The battery consists of 10 ANR26650m1-B high-performance Nanophosphate lithium iron phosphate (LiFePO4) cells, which deliver high power and energy density combined with excellent safety performance and extensive life cycling in a lighter weight, more compact package. To make this enjoyable, we will introduce a fault into one of the cells to demonstrate how it affects the pack as a whole.

ANR26650m1-B Nanophosphate lithium iron phosphate (LiFePO4) datasheet used for this project:

What is Fauly Cell ?

A faulty cell demonstates performance that is different than the other cell usually most cell will be displaying the same SOC ,temperature voltage level etc.but a faulty cell will show sign of overheating,faster discharge(due to reduced capacity or reduced OCV) oe will be unbalanced cell.this will be impact the performace of the entire pack as the faulty cell will limit the pack from utilizing its maximum potential.

in this project the faulty cell is repesenting by adding an extra external resistor.this will make the cell react diffirently then the other cells.

Simulink Model:

• in this model 1st, we give UDDS current profile to a battery pack with help of a signal builder block.
• UDDS cycle (current vs time) has been used to charge and discharge the batteries for a given period of time of 1370 sec.
• there is three modules have been connected together in series to make a 10-cell battery pack model.
• in cell no.6 a resister can be added to vary the rate of discharge.
• all cells are configured the same as the ANR26650m1-B cell .it means putting the same value in the datasheet.
• all cells are initially at 25 degrees c.a temp. the source is used to test the cell performance at 3 different atm.temperature,like At 25^oC,At 45^oC,At -10^oC .
• convective and conductive blocks have been added for heat transfer between blocks.

vehicle Current Model:

• In vehicle current requirement subsystem block,the signal builder block used to apply UDDS current profile and simulink-ps converter block used to convert the simulink signal to physical signal.connectin port block used to output the signal.

MATLAB Code:

clear all
close all
clc
f1 = xlsread('UDDS current profile (2).xlsx');
time = f1(:,1);
current= f1(:,2);

UDDS Current Profile in Signal Builder:

Module 1 [Cell 1-5]:

• In this module we used the 5 table based battery block in which we put the datasheet value on it.here i put the battery specification like, 2.5Ah capacity,initial temp.value is 298K etc.and this 5 cell are connected in series.
• also here we use the conductive heat transfer block in which we put the thermal conductivity is 401 W/(K*m),area is 10 m^2,and thickness is 0.1m.
• here we use the convective heat transfer block in which we put the heat transfer co-efficients is 20 W/(K*m^2),area is 10 m^2.and one end of this block is connected to thermal source and other is connected to perticular cell.
• here we use perfect insulator also.
• here we use temperature sensor to sense the temperature of cell and display the value in scope and dashboard.also it one end is connected to thermal reference.
• and SOC of every cell is also calculated by using add and gain block,and display the soc value in % in display block.

Module 2 [Cell 6]:

• In this module we used the table based battery block in which we put the datasheet value on it.here i put the battery specification like, 2.5Ah capacity,initial temp.value is 298K etc.and addition to that accross the battery terminal we use the 5 ohms resistor to show the this is the faulty cell.
• also here we use the conductive heat transfer block in which we put the thermal conductivity is 401 W/(K*m),area is 10 m^2,and thickness is 0.1m.
• here we use the convective heat transfer block in which we put the heat transfer co-efficients is 20 W/(K*m^2),area is 50 m^2.and one end of this block is connected to thermal source and other is connected to perticular cell.
• here we use perfect insulator also.
• here we use temperature sensor to sense the temperature of cell and display the value in scope and dashboard.also it one end connected to thermal referance.
• and SOC of every cell is also calculate by using add and gain block,and display the soc value in % in display block.

Module 3 [Cell 7-10]:

• In this module we used the 4 table based battery block in which we put the datasheet value on it.here i put the battery specification like, 2.5Ah capacity,initial temp.value is 298K etc.and this 4 cell are connected in series.
• also here we use the conductive heat transfer block in which we put the thermal conductivity is 401 W/(K*m),area is 10 m^2,and thickness is 0.1m.
• here we use the convective heat transfer block in which we put the heat transfer co-efficients is 20 W/(K*m^2),area is 10 m^2.and one end of this block is connected to thermal source and other is connected to perticular cell.
• here we use perfect insulator also.
• here we use temperature sensor to sense the temperature of cell and display the value in scope and dashboard.also it one end connected to thermal referance.
• and SOC of every cell is also calculate by using add and gain block,and display the soc value in % in display block.

SOC Calculation Model:

• here we use the 3 goto block and 3 from block and scope to analyze the change in soc of 3 different cell module.

Temperature Calculation Model:

• here we use the 3 goto block and 3 from block and scope to analyze the change in temperature of 3 different cell module.

To incorporate for the positioning of this cell(center of pack) certain changes have been made:

• the convective area is 10 m^2 for the remaining 9 cell,but has been increased to 50m^2 here.
• the ambient temperature provided from temperature source to the ramaining 9 cell are the same 298K,but has an increament of 7K for this cell.its means 305K.

Result:

A] At 25^oC:

1] SOC OF Different Module [%]:

• model 2 has a much steeper slope than the others bcoz of added 5 ohmc resistors.a load(in the form of a resistor) with a resistance of just 5 ohms will draw in more current compared to no added load.wich means a greater rate of discharge and hence more drainage of SOC.

2] Temperature Change In Module [K]:

• The initial temperature of the battery pack is set to 298K.
• the much steeper rise in temperature of module 2 compared to another module due to increased surface area contact and its position being in the center of the battery pack.
• although the ambient temperature supplied is 298K, module 2 reaches 305K (while the other cell is at 298K) for the aforementioned two reasons in addition to the fact that there is also added 5ohms resistance in mode 2.

3] Dashboard for Indication of SOC and Temperature Change:

• both the gauge shows the change in SOC and the change in Temperature.

B] At 45^oC:

1] SOC OF Different Module [%]:

• model 2 has a much steeper slope than the others bcoz of added 5-ohm resistor. a load(in the form of a resistor) with a resistance of just 5 ohms will draw in more current compared to no added load. which means a greater rate of discharge and hence more drainage of SOC.

2] Temperature Change In Module [K]:

• The initial temperature of batery pack is set to 298K.
• the much steeper rise in temperature of module 2 compared to another module due to increased surface area contact and its position being in the center of the battery pack.
• although ambient temperature supplied is 318K,module 2 reaches 325K (while the other cell are at 318K) for the aforementioned two reasons in addition to the fact that there is also added 5ohms resistance in mode 2

3] Dashboard for Indication of SOC and Temperature Change:

• both the gauge shows the change in SOC and the change in Temperature.

C] At -10^oC:

1] SOC OF Different Module [%]:

• model 2 has a much steeper slope than the others bcoz of added 5-ohm resistors.a load(in the form of a resistor) with a resistance of just 5 ohms will draw in more current compared to no added load. which means a greater rate of discharge and hence more drainage of SOC.

2] Temperature Change In Module [K]:

• The initial temperature of batery pack is set to 298K.
• much steeper fall in temperature of module 2 compared to another module due to increased surface area contact and its position being in the center of the battery pack.
• although the ambient temperature supplied is 263K, module 2 reaches 270K (while the other cell are at 263K) for the aforementioned two reasons in addition to the fact that there is also added 5ohms resistance in mode 2

3] Dashboard for Indication of SOC and Temperature Change:

• both the gauge shows the change in SOC and the change in Temperature.

Submitted By:

Himalaya Singh

8/12/2022