Project 2

PROJECT - 2

AIM : To find maximum heat generation of the battery & SOC of the battery at 2*104 seconds of the battery operation.

GIVEN :

Battery Resistance = 0.0005 `Omega`

Delta Time = 0.1

Entropic Factor = 2.

Time	Time Step	Battery Current
00:00.4	0.1	-0.9632
00:00.5	0.2	-0.952
00:00.6	0.3	-0.9072
00:00.7	0.4	-0.9632
00:00.8	0.5	-1.0304
00:00.9	0.6	-0.9632
00:01.0	0.7	-1.0304
00:01.1	0.8	-1.008
00:01.2	0.9	-0.9856
00:01.3	1	-0.9632
00:01.4	1.1	-0.9184
00:01.5	1.2	-0.9296
00:01.6	1.3	-0.9296
00:01.7	1.4	-0.9296
00:01.8	1.5	-0.9184
00:01.9	1.6	-0.9408
00:02.0	1.7	-0.896
00:02.1	1.8	-0.9072
00:02.2	1.9	-0.9072
00:02.3	2	-0.9408
00:02.4	2.1	-0.9296
00:02.5	2.2	-0.9296
00:02.6	2.3	-0.9968
00:02.7	2.4	-0.9968
00:02.8	2.5	-0.9408
00:02.9	2.6	-0.9408

THEORY :

• Heat Generation in Battery.

There are two sources of heat generation in a battery -

1. Joule Heat :	It is the physical effect by which the passing of current through an electrical conductor produces thermal energy. Also called resistive heating, ohmic heating. It is given by - `I^2*R*t` Where, I = Electric current through conductor (A). R = Resistance (`Omega`); t = elasped time (s)
2. Entropic Heat :	It is the rate of change of battery's open circuit voltage wrt. temperature.. It is a function of temperature and SOC. For this model purpose it is considered as a factor of 2 to Joule Heat.

`therefore\ \Heat\ \Gen\erated = Jou\l\e\ \Heat + Entro\p\ic\ \Heat`

• State Of Charge (SOC) of Battery.

It is defined as the ratio of the available capacity Q(t) and the maximum possible charge that can be stored in a battery.

`SOC = (Q_t)/(Q_m)`

A Simulink model is made for SOC measurement : -

Blocks Used-

1 . Battery	It implements a generic battery block for most popular battery types. For this model :- Cell Type - Lithium ion Nominal Voltage : 7.2 V Rated Capacity : 5.4 Ah Maximum cell Voltage : 8.3 Internal Resistance : 0.0005 `Omega`
2. Bus Selector	- This blocks accepts a bus as input and outputs the elements selected by user separately. - In this model Measurement Bus from battery is taken and connected with scope for 2 elements viz. SOC & Current.
3. Controlled Current Source	- It converts its input signal into an equivalent current source. - The current generated is driven by the input signal of the block.
4. From Workspace	- It is used to read data from MATLAB workspace. - In MATLAB workspace data is imported from excel sheet.
5. Powergui	- It sets the simulation type, simulation parameters and preferences. - For this model continuous simulation type is selected.

SIMULINK MODEL :

- In this model, A drive cycle source/signal is connected to battery via a Controlled Current Source block to control the current via the battery according to the input cycle.

- Output from battery is given to bus selector and then to scope and display.

- The model is run for 208 seconds to measure SOC.

OBSERVATIONS :

• Max Heat Generated:-

Max Battery Current = -0.896

Time = 2 min = 120 seconds.

Joule Heat = `I^2*R*t` = `(-0.896)^2*0.0005*120 = 0.04816\ \kJ`

Entropic Heat = 2*(Joule Heat) = 0.09632 kJ

Total Heat Generated = Joule Heat + Entropic Heat

= 0.04816 + 0.09632

Max Heat Generated = 0.14448 kJ

• SOC Measurement:-

SOC = 98.98 %

- When the model was run for 208 seconds, the SOC is 98.98 %.

CONCLUSION :

Maximum Heat Generated for the given drive cycle is 0.14448 kJ.

Battery SOC at 208 seconds for the given drive cycle is 98.98%.

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