Project 2 Thermal modeling of battery pack

PROJECT 1:

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

Introduction:

This project will simulate the thermal effects of a 10S1P Lithium-ion battery pack, which consists of 10 Lithium-ion cells connected in series, to explore the performance of the pack. To make it interesting, a fault has been introduced in one of the cells to demonstrate the effect of the faulty cell on the entire pack.

Faulty cell:

 A faulty cell demonstrates performance that is different than the other cells. Usually most cells will be displaying the same SOC, temperature, voltage levels, etc, but a faulty cell will show signs of overheating, overcharging, faster discharge (due to reduced capacity or reduced OCV), or will be an unbalanced cell. This will impact the performance of the entire pack as the faulty cell will limit the pack from utilizing its maximum potential.

Model Construction:

1. Totally 3 modules(Battery1 to 5 , 6(fault) ,Battery7 to 10) have been connected together in series to make a 10 cell battery model
2. Signal Builder Block Uses UDDS cycle as a source,which is used to charge/discharge the batteries for required Period.
3. A resistor can be added to vary the rate of discharge
4. All cells are initially at 25 degree C
5. A temperature source is used to test the cell performance at four ambient temperatures: -10 degree C, 0 degree C, 25 degree C, 45 degree C
6. Convective and conductive blocks have been added for heat transfer between blocks.

1) Vehicle Load UDDS Data:

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.

 Udds Current Supply is given Through Signal Builder Block to Controlled Current Source.

2) Battery 1 to 5 in series:

1. 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.
2. also here we use the conductive heat transfer block in which we put the thermal conductivity is 401 W/(K*m),area is 0.01 m^2,and thickness is 0.1m.
3. 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.
4. here we use perfect insulator also.
5. 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.

3) Battery 6 in series: (Fault Cell)

1. 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.
2. also here we use the conductive heat transfer block in which we put the thermal conductivity is 401 W/(K*m),area is 0.01 m^2,and thickness is 0.1m.
3. 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.
4. here we use perfect insulator also.
5. 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.

4) Battery 7 to 10:

1. 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.
2. 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.
3. 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 0.01 m^2.and one end of this block is connected to thermal source and other is connected to perticular cell.
4. here we use perfect insulator also.
5. 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.

Overall Simulink Model:

1. The convective area is 0.01 m^2 for the remaining 9 cell,but has been increased to 10 m^2 here.
2. 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.

Case 1: Temp at 263.15:

Both the gauge showing the change in SOC and change in Temperature for 263.15 K.

Case 2: Temp at 273:

Both the gauge showing the change in SOC and change in Temperature for 273 K.

Case 3: Temp at 283:

Both the gauge showing the change in SOC and change in Temperature for 283 K.

Case 4: Temp at 298.15:

Both the gauge showing the change in SOC and change in Temperature for 298.15 K.

Resultant Scope:

Soc:

Module 2 has a much steeper slope than the others bcoz of added 10 ohm resistor.a load(in the form of resistor) with a resistance of just 5 ohms will draw in more current compared to no added load.wich means greater rate of discharge and hence more drainage of SOC. 

Temp:

1. Initial temperatre of batery pack is set to 273K.
2. Much steeper rise in temperature of module 2 compared to other module due to increased surface area contact and its position being in the center of the battery pack.
3. Although ambient temperature supplied is 273K,module 2 reaches 298.15 K for the aforementioned two reasons in addition to the fact that there is also added 10 ohms resistance in mode 2.

Conclusion:

Thus, simulation with thermal effects and compare life cycle performance at various temperatures, charge & discharge rates using MATLAB is modeled and analysed.