Project 2
Aim :- A)To find maximum heat generation of battery .
B) The SOC of the battery at 2 *104second of the battery operation
Specification :- Battery resistance =0.5 mohm , delta time =0.1 , Entropic factor =2
1. The max heat generation of the battery
There are 2 heat sources for the battery heat generation
- Joules heat
- Entropy heat
Heat generated = Joules Heat + Entropy Heat
Joules Heat :
froms ohms law we know that
V = IR
when a current flowing through a resistance, there is a heat dissipated in the resistor. This heat dissipation is called Joule heating. Joule heating is also known as ohmic heating.
Power,
P = V*I = I*I*R = I^2*R
Heat,
H = ∫P.dt with the limits of time 0 to t
H = I^2*R*t
Joule heat,
H = I^2*R*t
where. p = Power
V = Voltage
I = Current
R = Resistance
H = Heat
t = Time
The heat Generated in the Reisitor is-
- Directly proportional to the square of the current flowing through it
- Directly proportional to the resistance
- Directly proportional to the time for which the current flows through it.
Entropy Heat:
The heat generation due to entropy change inside a battery occurs when electro chemical reactions are performed. The entropy heat is reversible heat resulting from change in open circuit voltage with respect to temperature at two Electrodes.
Given data
Battery resistance = 0.5 mOhm = 0.0005 Ohm
Maximun current = -0.896 A
Max current time = 1.7 sec
Entropic factor = 2
Total heat generation = Joule heat + Entropy heat
The maximum heat generation in the battery pack
Max heat generation = Max Joule Heat + Entropy factor
Max Joule Heat = I^2 *R*t
Max Joule Heat = -0.8962⋅0.0005⋅1.7">−0.8962⋅0.0005⋅1.7-0.8962⋅0.0005⋅1.7
Max Joule Heat = 0.0006823936J">0.0006823936J0.000682393
Max heat generation = 0.0006823936 + 2 = 2.0006823936 Jouls
The Max heat generation is 2.0006823936 Jouls
2. The SOC of the battery at 2 *104second of the battery operation:
The SoC refers to the State of Charge of the battery, which is the capacity percent left in the battery which can be used. It a very important thing which tells about the battery status which helps in using the battery in a proper manner.
The SoC can be measured in different ways. Some of them are listed below
- Voltage Translation Method (VT)
- Coulamb counting method (CC)
- Combination of VT and CC
The VT and CC has its own advantages ad disadvantages so to get accurate value we have to use the Combination of VT and CC.
Voltage Translation Method (VT):
It is measured by Open Circut Voltge of the battery and compared it with the Data sheet of the battery and SoC is estimated. It cannot used while the battery is in operation.
Coulamb counting method (CC):
It is calculated by the formula
SoC = total charge input / Max capacity of the battery
Total charge input = charge current * time (H)
Or
Z(t) = Z(0) - 1/Cn ∫ Ni*i(t) dt with thw limits of 0 to t
where, Cn = Battery Nominal Capacity
Z(t) = State of charge
i(t) = Instantansous cell current
t = time
Ni = coulomb efficiency
Z(0) = initial state of charge
+ for discharging
- for charging
Given data :-
here we are converting time to seconds are as shown below :-
| Time | Battery current |
| 4 | -0.9632 |
| 5 | -0.952 |
| 6 | -0.9072 |
| 7 | -0.9632 |
| 8 | -1.0304 |
| 9 | -0.9632 |
| 60 | -1.0304 |
| 61 | -1.008 |
| 62 | -0.9856 |
| 63 | -0.9632 |
| 64 | -0.9184 |
| 65 | -0.9296 |
| 66 | -0.9296 |
| 67 | -0.9296 |
| 68 | -0.9184 |
| 69 | -0.9408 |
| 120 | -0.896 |
| 121 | -0.9072 |
| 122 | -0.9072 |
| 123 | -0.9408 |
| 124 | -0.9296 |
| 125 | -0.9296 |
| 126 | -0.9968 |
| 127 | -0.9968 |
| 128 | -0.9408 |
| 129 | -0.9408 |
As we know we have to find SOC upto 208 seconds but data is available upto 129 second . Therefore , from 129 to 208 seconds the battery current is same .
Simulink model explanation
Here we use
1. Signal builder =to give input signal as bateey current and their timing
2. Battery
3. Scope for output waveform
4. Bus selector for SOC
5. Power gui for some continuous calculation and plotting
6. Controlled current source .
We gave initial SOC of battery = 30%
Afetr run the simulink model The output scope is as shown below :-
highest current value=-0.896
battery capacity=1 Ah
Therefore we can say that the charging process is done above 3% i.e 30 to 33.5 % .
Charge and Discharge command or Siganal to run the Constant Currnet source, so that the current will flow in and out according to the signal. + signal to chagrge and - for discharge. The total time for the run is taken as 2*104 = 208 sec
Now , we will see signal builder with input data from data sheet upto 129 seconds :-
This is drive cycle .
Result and Conclusion:
1. The max heat generation of the battery
The Max heat generated in which the current flowing in and out i.e., charge and discharge due to internal resistance and chemical reaction during charging and discharging of the battery the heat is generates of 2.0006823936 Joules
2. The SOC of the battery at 2 *104second of the battery operation:
Initially the battery SoC is taken as 30% so it started and according to the current signal i.e., charging , if the charging happens the battery SoC is increasing and when it is discharging SoC is decreasing.