Project 2

Using MATLAB/simulink and the drive cycle from the attached excel sheet, find-

1. The max heat generation of the battery
2. The SOC of the battery at 2 *104second of the battery operation

Consider the battery resistance is 0.5 mOhm, delta time is 0.1 and entropic factor is 2

AIM -To find Maximum Heat generation by the battery and Build the Simulink model for SOC of the battery at 2*104 second of battery operation.

THEORY -

Heat generated = joules heat + entropy heat

joules heat ,from ohms law we know that

V=IR

when the current flowing through a resistance, there is a heat dissipated inn the resistor this heat dissipation is called joules heating. Joules heating is also known as ohmic heating.

power P=V*I=I^2*R

Heat H=∫P.dt with the limits of time 0 to t

H=I^2*R*t

where,

P=power

V=voltage

I=current

R=resistance

H=heat

T=time

Entropy heat - The heat generation due to entropy change inside a battery occurs when electro chemical reaction are performed. the entropy heat is reversible heat resulting from change in open circuit voltage with respect to temperature at two electrodes.

batterry resistance = 0.5m ohm = 0.0005ohm.

Calculation -

Maximum current = -0.896 A

Maximum current time = 2 min = 120 sec

Entropic factor = 2

Total heat generation = Joule heat + Entropy heat

The maximum heat generation in the battery pack is given by

Maximum heat generation = Max Joule Heat + Entropy factor

Maximum Joule Heat = I^2 *R*t

Maximum Joule Heat = (-0.896)^2*0.5*120

= 48.168 mJ

Maximum heat generated = 48.168 mJ +2

=50.168 mJ

The Maximum Heat generation is 50.168 milijoules .

2. The SOC of the battery at 2 *104second of the battery operation.

The state of charge (SOC) is a measurement of the amount of energy available in a battery at a specific point in time expressed as a percentage. The SOC provides the user with information of how much longer the battery can perform before it needs to be charged.

SIMULINK MODEL -

Blocks Used -

1. Generic Battery:

Implements a generic battery model for most popular battery types. Temperature and aging (due to cycling) effects can be specified for Lithium-Ion battery type.The Battery Parameters selected are 7.2V 5.4Ah with initial SOC of 50%.Also the fully charged voltage of battery is 8.3807V and considering all the parameters in Battery as default.

2. Controlled Current source -

Converts the Simulink input signal into an equivalent current source. The generated current is driven by the input signal of the block. You can initialize your circuit with a specific AC or DC current.

3. Bus Selector -

This block accepts a bus as input which can be created from a Bus Creator, Bus Selector or a block that defines its output using a bus object. The left listbox shows the elements in the input bus. Use the Select button to select the output elements. The right listbox shows the selections. Use the Up, Down, or Remove button to reorder the selections. Check 'Output as virtual bus' to output a single bus.

4. Signal Builder -

The Signal Builder block allows you to create interchangeable groups of piecewise linear signal sources and use them in a model. You can quickly switch the signal groups into and out of a model to facilitate testing. In the Signal Builder window, create signals and define the output waveforms.

The data of Time Vs Battery current is loaded in the signal bulider. Firstly open the signal bulider then go to signal then select custom and then put Time values and Y- values in it.Then we obtain the above signal.

5. Resistor -

The resistor is uesd to limit the flow of current to the battery. From RLC branch, only resistor is selected and putting its value as 0.5miliohm i.e 0.0005. Resistor is connected between the controlled current source and Battery.

6. Scope and Powergui -

Scope displays the output graph and powergui block set simulation type, simulation parameters, and preferences.

Explanation:

• The above signal is given as a input to the battery block. The Excel sheet is loaded into the Signal Builder block and signal builder block ouput is given to the controlled current source.
• The Simulation stop time is 2*104 seconds ie 208Seconds.
• The Signal builder acts as a load to the battery.
• The Battery Block shows the SOC, Voltage and Current through the bus selector block.
• The output is displayed through Scope block. It shows the nature of SOC%, Current and Voltage .

RESULT -

Initially the Battery is charged near to its full capacity.As the load (data of signal builder) is applied to it then the battery SOC starts decreasing and reaches near to 99% after completion of 208 sec of simulation time.

The current waveform is same as the waveform which is obtained at the signal builder. It increases and decreases according to the time steps.

The fully charged voltage of battery is 8.3087V so it is clearly showing in the above graph and as the battery gets discharged by handling load ,voltage of battery gets also decreased. It reaches near to 8.1V as shown in the above graph.

CONCLUSION -

I this project we calculated the Maximum Heat generation of battery. Also we design a simulink model for the SOC of the battery at 2 *104second of the battery operation and simulated the battery SOC, current and voltage for the given drive cycle .