Project 2 Thermal modeling of battery pack

A default MATLAB Simulink Model of Battery Pack which I used for 10-cell battery pack thermal modelling.

A detall design of MATLAB Simulink model for thermal modelling is given as-

Cell Subsystem

Cell subsystem basically consist of a Thermal Model and Lithium Cell 1RC block which calculate the temperature and thermal effect for cells 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 i.e. y = u.* gain. Another block are voltage sensor and current voltage source.

The voltage sensor block represents an ideal voltage sensor, that 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, 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: This 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 models 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 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. The measurement is positive when 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 is 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 cell's main branch voltage source, and determines values for capacity (C) and state of charge (SOC). The defining equations depend on cell temperature, T.

Thermal Behaviour and Fault setup

Lithium lon 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 299.1 K

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 299.1 K

• Capacity (Ahr) - Capacity_LUT*0.95

• Em open-circuit voltage (volts) - Em_LUT"0.9

• RO terminal resistance (ohms) - RO_LUT 5

• R1 cell resistance (ohms) = R1_LUT"5

• Cl capacitance (farads) = C1_LUT*0.95

For cell 06 to 10

• Number of series-connected cells are 5

• Initial Temperature is 299.1K

Screenshot of dialogue box with detail changes

Cyclic Charge/ Discharge Profile-

Teamperature Mesurement Subsystem-

from and goto blocks-

The Goto block passes its input to its corresponding From blocks. The input can be a real- or complex-valued signal or vector of any data type. From and Goto blocks allow you to pass a signal from one block to another without actually connecting them.

The From block accepts a signal from a corresponding Goto block, then passes it as output. The data type of the output is the same as that of the input from the Goto block. From and Goto blocks allow you to pass a signal from one block to another without actually connecting them.

Temperature Source-

Fron this block we can simulate model for different temperature

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

SOC Estimation-

The Coulomb counting method measures the discharging current of a battery and integrates the discharging current over time in order to estimate SOC

This subsystem takes current as input and gives the battery SOC % as output. A current sensor block is used and connected for soc estimation

This ckt estimates the battery SOC % using coulomb counting method. It takes current as the input and gives SOC% as output. Initial SOC of the battery is assumed to be 100% (1)

example shows how to simulate a 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 temperatures

Results for Various Temperatures

1) results at 300 k (ie 26.85°C)

2) results at 310 k (ie 36.85°C)

3) results at 324 k (ie 50.85°C)

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

1-4 cells are normal cell 5 th cell is faulty 6-10 cell is normal cell as we are simulating thermal effect on we give Cyclic Charge/Discharge Profile to circuit the waveform you can see above results all conditions it is same but when ckt is run on this drive cycle profile as 5th cell was faulty it will show temperature rise high than any other cell and the life cycle of cell get reduced and cell even can get damage

1) So as we give temp of results at 300 kie 26.85°C the 1-4 and 6-10 cell temp is near to 316k

but 5th faulty cell temp goes to 330k ie 56.85°C and the drive cycle is shown which is Cyclic Charge/ Discharge drive cycle

2) In condition Second, we give temp 310 k ie 36.85°C and 1-4 and 6-10 cell temp is near to 326 k but 5th faulty cell temp goes to 340k ie 66.85°C and the drive cycle is shown which is Cyclic Charge/ Discharge drive cycle

3) In Third condition, we give temp 324 k ie 50.85°C and 1-4 and 6-10 cell temp is near to 340 k but 5th faulty cell temp goes to 354k ie 80.85°C and the drive cycle is shown which is Cyclic Charge/ Discharge drive cycle

conclusion-

we simulated the thermal effect and compared at various temperature faulty cell temp rise more than normal cell charge and discharge cycle given and due to temp rise it can damage the cell and reduce the performance of the battery.