Project 2 Thermal modeling of battery pack

Aim :-

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.

Introduction :-

The lithium oin batteries are widely used as energy sources in different hybrid and electric vehicle however the operatrion characterstics of the battery in such vehicle are strongly dependent on the operation temperature and therefore with purpose to improve these characterstics a good thermal control system should be utilised.

The temperature of a lithium battery cell is important for its performance efficiency safety and capacity and is influenced by the environmental temperature and by the charging and discharging process itself. Therfore a thermal model of the battery is used in order to calculate and estimate the cell temperaute.

So for 10 cell series lithium ion battery here i used MATLAB simulink for finding thermao effect and life cycle performance related to temperature charge and discharge'

Lithium ion battery pack with fault is to simulate a battery pack consisting of multiple series connected cells in an efficient manner' It also shows how a fault can be intoduced into one of the cells to see the impact on battery performance and cell temperatures. For efficency identical series connected cell are not just simply modelled by connecting cell models in series. instead a single cell is used and the terminal voltage scaled up by the number of cell. The fault is represented by changing the parameters for the cell 5 fault subsystem reducing both capacity and open circuit voltage and increasing the resitance values.

A default MATLAB simulink model of battery pack which i sed for 10 cell battery pack thermal modelling.

A detail design of MATLAB simulink model for thermal modelling is given as :-

Cell 01 to 04 subsystem :-

Cell subsystem basically consist of a thermal model and lithium cell 1RC block which calculate the temperature and thermal effect for cell and overall calculate for the battery pack.

The block which are inside the cell subsystem are PS gain block which multiplies the input physical signal by a costant ie y=u*gain. Another block are voltage sensor and current voltage source.

The voltage sensor block represented an ideal voltage sensor, that is a device that convets voltage measured between any electrical connections in to a physical signal praportional to the voltage.

Current voltage source represent an ideal voltage source that is powerfull enough to maintain the specified voltage at its output regarless of the current passing through it. The output voltage is V=Vs, where Vs is the numerical value presented at the physical signal port.

Thermal Model subsytem :-

The important block which is inside the thermal model subsytem are :

• Thermal Reference : This block represents a refference point in a thermal network where the temperature is equal to absolute zero
• Controlled heat flow rate source : This block represents an ideal energy source in a thermal network that can maintain a controlled heat flow rate regarless of the temperature differrenc. The heat flow rate flows from port A to port B.
• Thermal Mass : This block models internal energy storage in a thermal network. The rate of temperature increase is praporational to the heat flow rate intl the material and inversely praportional to the mass and specific heat of the material.
• Temperature sensor : This block measures temperature in a thermal network. There is no heat flow through the sensor. The physical signal port T reports the temperature difference across the sensor.

Screen shot of dialogue box with detail changes :

Results :-

Simulation based on different cell temperature

In this simulation i set ambient temperature 299.1K or 25.95C and another cell temperature are as below:

Test 1 -

Cell temperature

SOC -

Test 2 -

Cell temperature -

SOC -

Test 3 -

cell temperature

SOC -

Test 4 -

cell temperature

SOC -

Test 5 -

cell temperature

SOC -

Conclusion :-

The flow of heat is decreased at constant and minimum temperature that is 309K for different temperature based.

Based on diffenrent temperature we will see changes in conduction and convection.

There is slightly changes in cyclic charge and discharge of cell wich i fixed at 50A as peak amplitude

As i set fault in cell 5 and we can see that there is lots of fluctuation and temperature rise in cell 5 as compared with other cells connected in series.

SOC for all different temperature are same there is no changes in SOC.