Project 2 Thermal modeling of battery pack

Introduction

The Lithium-ionbatteriesare widely used as energy sources in different hybrid and electric vehicle, however, the operation characteristics of the battery in such vehicle are strongily dependent on the operation temperature and therefore, with purpose to improve these characteristics a good thermal control system shouldbe utilized.

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. Therefore, a thermal model of the battery is used in order to calculate and estimate the cell temperature.

So, for 10-cell series lithium ion battery here Il used MATLAB Simulink for finding thermal effect and life cycle performance related to temperature, charge and discharge.

Lithium-lon 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 introduced into one of the cells to see the impact on battery performanceand cell temperatures. For efficiency, identicalseries-connected cells 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 cells.The fault is represented by changing the parameters for the Cell 5 Fault subsystem,reducing both capacityand open-circuit voltage, and increasing the resistance values.

A deftail design of MATLAB simulink model of battery pack which i used for 10- cell battery pack thermal modelling

A detail desing 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 1 RC 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 representsa 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 portB.
• 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 inverselyproportional 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 1 RC 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.

The above is the parameter of the cell and the number of the cell need to be give as per to our qustion numbers. and here there is we need 10 cell and we divide it into 3 cell in which the 5 cell is a faulty cell and at the both top and bottom we given 4 cell each .These changes are made in the parameters of each cells parameter.

Graphs:

this is the out put graph which we can observe from the help desk menu in the simulink /MATLAB

a)cell temperature

all the three the cell having the same temperature at the start which is at 299.1 k.but in the beginning few seconds of simulation cell no 5 oscillates with more the cell 4 and 10 because its design with fa ult and ranging to higher temp then cell 4 and 10.after a time period of around 1300 sec both the cells getting are unfollowing the temperature line which was following the same temperature rate,cell no 4 and 10 having approximately 315(cell 04 having quite less temp then cell 10 because of no of the cell are different) k at the end of the simulation and the cell no 5 achieving the higher temperature of around 328 k

b)SOC:-

the soc graph following the sinusoidal waveform structure amd fluctuating after 297 seconds and this waveform achieving the values of more than 100.6 soc

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 tempertaure rise it can damage the cell and reduce the performance of the battery