Project 2
AIM:
To find the max heat generation of the battery & the SOC of the battery at 2 *104 second of the battery operation using MATLAB/simulink and the drive cycle from the attached excel sheet.
a) Calculation of Maximum Heat generation of the battery:
Heat generated = Joule Heat + Entropy Heat
Entropy Heat is given as 2.
Therefore, Heat generated = Joule Heat + 2
Now we have to find out the Maximum Heat generated which is given by the formula,
Maximum Heat generated = Maximum Joule Heat + 2
We know that
Power = V *I
And from ohm's law we get, V = I * R
So, Power = I * R *I
Power = I^2 * R
Heat = int (P) dt which gives
Joule Heat = I^2 * R * t
Maximum Current from the table is -0.896 & time is 120 seconds
So, Maximum Joule Heat = I^2 * R * t
Resistance is given as 0.5 milli ohm
Maximum Joule Heat = (-0.896)^2 * 0.5 * 10^-3 * 120
Maximum Joule Heat = 0.048 Joules
Now, Maximum Heat generated = Maximum Joule Heat + 2
= 0.048 + 2 = 2.048 J
Maximum Heat generated = 2.048 Joules
Therefore, the maximum heat generation in the battery pack will be 2.048 Joules.
b) SOC: The state of charge is defined as the ratio of the available capacity Q(t) and the maximum possible charge that can be stored in a battery, i.e., the nominal capacity Qn. A fully charged battery has SOC 1 or 100% while a fully discharged battery has an SOC of 0 or 0%.
SOC Estimation Techniques:
1) Voltage Translation Method:
The battery voltage (open circuit voltage) is used to determine the state of charge of the battery pack. The voltage translation method is used in applications like consumer electronics (battery bank, trimmer, torch light) & small energy storage systems. The LCD & LED are used to determine the SOC. The errors in voltage translation methods are voltage fluctuation, noise in the system & cell chemistry. So, it is not used in electric vehicles.
2) Coulomb Counting Method:
The Coulomb counting method measures the discharging current of a battery and integrates the discharging current over time in order to estimate SOC. Coulomb counting method is done to estimate the SOC(t), which is estimated from the discharging current, I(t), and previously estimated SOC values, SOC(t-1). SOC is calculated by the following equation:
SOC(t) = SOC(t-1) + (I(t)/Qn)dt
But there are several factors that affect the accuracy of Coulomb counting method including temperature, battery history, discharge current, and cycle life.
Simulink Model:
Signal builder block is used to make the drive cycle given which is given the current input to the battery through controlled current source. The bus selector block is used to extract the values of SOC, voltage & current which is then send to scope to view the result.
Battery parameter is chosen as default value.
Signal Builder:
The given signal is imported from the excel sheet given.
RESULT:
The simulation is run for 208 seconds.
The SOC after 208 seconds is found to be 99 %
CONCLUSION:
1) Thus from the calculation the maximum heat generation of the battery is 2.048 Joules.
2) The SOC of the battery at 2 *104 second of the battery operation is 99 %