Challenge

Project 2 Thermal modeling of battery pack

SSumit Mullick9 Jan 2022

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.

ans.

Introduction

Delhi team and battery the widely used as energy sources in different hybrid and electric vehicle, however the operation characteristics of the battery in search vehicle are strongly dependent on the operation temperature and therefore with purpose to improve these characteristics 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 band by charging and is charging process itself therefore a thermal model of the battery is used in order to calculate an estimate the cell temperature.

So for a a 10 cell series lithium ion battery here I have used matlab simulink for finding thermal effect and life cycle performance related to temperature charge and discharge.

Lithium ion battery pack with faulty is to stimulate the battery pack consisting of multiple series connected cells in an efficient manner. It also shows how a fault can be introduced into one of the cells to see the impact on battery performance and cell temperature. For efficiency identical series connected cells model by connecting cell models in series. Instead a single cell is used and terminal voltage scaled up by the number of cells. The fault is represented by changing the parameters for the cell 5 fault subsystem reducing both capacity and open circuit voltage and treating the resistance values.

A default matlab simulink model of battery pack which I used for 10 cell battery pack thermal modelling is as follows.

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

Cell 01 to 04 Subsystem

Chal subsystem basically consists of a thermal model and Lithium cell 1RC block which calculate the temperature and thermal effect for sales 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 constant ie y=u.*gain , another block of voltage sensor and current voltage source.

The voltage sensor block represents an ideal voltage sensor, that is, is a device that converts voltage measured between any electrical connections into a physical signal proportional to the voltage.

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

Thermal model subsystem

The important block which is inside the thermal model subsystem are:
Thermal reference - the block represents a reference 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 regardless of the temperature difference. The heat flow rate is set by the physical signal port S. A Positive heat flow rate flows from port A to port B.

Thermal mass - this block Model is internal energy storage in a thermal network. The rate of temperature increase is proportional to the heat flow rate into the material and inversely proportional to mass and specific heat of the material.

Temperature sensor - this block measure 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. The measurement is positive and the temperature at Port A is greater than the temperature at Port B.

Lithium cell 1RC subsystem

This block basically consists of capacitance value table which depends on an external physical signal inputs SOC and T, it is assumed that the capacitance value slowly varying with time and hence the equation i=C*dv/dt holds.

Resistance value (R) table which depends on an external physical signal inputs SOC and T.

Voltage value(EM) which implements the cells main branch voltage source, and determine the values for capacity(C) and state of charge(SOC) . The defining equations depend on cell temperature T.

Thermal behaviour and fault setup

Lithium-ion Cell one RC branch equivalent circuit detail for 10 cells.

for cell 01 to 04

Number of series connected cells are 4

Initial temperature is 299.1K

For cell 05(fault setup) In this cell I have done some changes in Electrical system of cell so that we can see the fault.

Number of series connected cells are 1

Initial temperature is 299.1K

capacity(A*hr) = Capacity_LUT*0.95

Em open-circuit voltage(volts) = Em_LUT*0.9

R0 terminal resistance = RO_LUT*5

R1 cell resistance = R1_LUT*5

C1 capacitance = C1_LUT*0.95

for cell 06 to 10

Number of series - connected cells are 5

Initial temperature is 299.1K

screenshot of the dialog box

cell 1 to 4

cell5(fault)

cell 6 to 10

Dadar block which are used in lithium ion battery pack are:

temperature source: This block represents an ideal energy source in a thermal network that can maintain a constant Absolute Temperature at forth regardless of the heat flow rate.

Here I used is blocked for ambient temperature and which I set as 299.1K.

Convective heat transfer:
This block Model heat transfer in thermal network by Convection due to fluid motion. The rate of heat transfer is proportional to the temperature difference heat transfer Coefficient and surface area in contact with the fluid.

Here I use three blocks for convection:

Conductive heat transfer:
This block Model heat transfer in a thermal network by conduction through a layer of material. The rate of heat transfer is governed by 4 years law and it is proportional to the temperature difference, material thermal conductivity, area normal to the heat flow direction and is inversely proportional to the layer thickness.

The conduction is done from two set of blocks are used for 01-04 another is used for cell 06-10.