Project 2

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

1. The max heat generation of the battery 

Answer :

Given data

Maxmium Heat = I^2  X Rt

Current (I)=-0.896

Resistance = 2 mill ohm =0.002 ohm

Time(t)= 2 mints= 120 sec

Maxmium Heat = I^2  X Rt 

Maxmium Heat = -0.896^2 X 0.002 X 120

=0.802816 X 0.002 X 120 =0.19267584

Entropic heat = Maximum Heat X 2

Entropic Heat = 0.19267 +  2 = 2.1926 milli joule

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

Given data

Maxmium Heat = I^2  X Rt

Current (I)=-0.896

Resistance = 0.5 mill ohm

Time(t)= 2 mints= 120 sec

Maxmium Heat = I^2  X Rt 

Maxmium Heat = (-0.896) ^2 X 0.5  X 120

Maximum joule heat generated = 48.16 milli Joule

Entropic factor= 2

Maximum heat generated= max joule heat + entropic heat

                                        = 48.16 + 2

Maximum heat generated =50.16 milli joule

Maximum of heat generation of battery is 50.16 milli joule

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Answer :

In simple words (The State of Charge) is your fuel gauge for battery-operated vehicles or E-vehicle. It is the real-time or actual capacity of the battery compared to its full capacity. Just like your cellphone battery, it is measured in terms of percentage (%). E.g., 100% SoC means the battery is fully charged to its capacity, and 0% SoC means it’s fully discharged.

The importance of calculating SoC

I will admit that the estimation of the SOC of a battery is not an easy task depending. It definitely varied based on the battery type and the type of application that is using the battery. However, there has been good research work and development in past years to improve the estimation of SOC accuracy. Accuracy in SOC estimation is one of the important tasks for battery management systems, which will help improve system reliability and performance and improve the battery life cycle.

In general SoC of the battery is calculated by the simple formula given below, i.e.ratio of real-time charges present in a battery(Qt) to full battery capacity charges (Qn).

SoCt=Qt/Qn

Though, if you can actually estimate precise SOC calculation, then you will save yourself from unpredictable system blockage. It will prevent you from overcharging your batteries, which, in reality, damages your battery’s internal structure.

However, you cannot estimate the accurate SOC under every condition because it involves complicated chemical and physical processes.

Voltage Method

Under a controlled environment, you can determine the real-time pending capacity of a battery, SOC, by using a discharge test method. In the voltage method, battery voltage is converted to equivalent SOC value using the battery’s predefined discharge curve (voltage vs. SOC). Anyhow, the battery’s electrochemical kinetics and temperature affect the battery’s voltage.

You can rely on the voltage method by using a lookup table of the battery’s open-circuit voltage (OCV) vs. temperature. As well as, by a correction term proportional to the battery current and by compensating the voltage reading.

The voltage method is however difficult to implement because it needs a stable voltage range for the batteries. In addition, this discharge test is very time-consuming because it includes a consecutive recharge when there are many applications.

Errors in this method are shown below

• Voltage fluctuation
• Noise in the system
• Cell chemistry.

SoC Estimation by Coulomb Counting is based on the measurement of the current and integration of that current over time.

The State of charge (SoC) of a battery cell is required to maintain it’s safe operation and lifetime during charge, discharge and storage. However, SoC cannot be measured directly and is estimated from other measurements and known parameters. This leads to errors in the estimated SoC and that means it is not possible to fully exploit the full capability of the cell.

Coulomb counting gives a relative change in SoC and not an absolute SoC. If you measure the current over a given time step you have a measure of the number of Ah that have left or been received by the battery.

The Coulomb counting method measures the discharging current of a battery and integrates the discharging current over time in order to estimate SOC. The coulomb counting method is done to estimate the SOC with respect to time. Which is estimated from the discharging current I(t), and previously estimated SOC values, SOC(t-1). SOC is calculated by the following equation.

where:

SoC(t)= estimated State of Charge at time, t

SoC(t-1)= previous State of Charge at time t-1

I(t)= charging or discharging current at time, t

Q_n= battery cell capacity

Δt= time step between t-1 and t

But there are several factors that affect the accuracy of the Coulomb counting method including temperature, battery history, discharge current, and life cycle. The coulomb counting method depends on the recording of the current noise only. The signal is filtered with a high pass filter with a cut-off frequency of 0.01Hz.

If you want to know the absolute SoC you need to know the starting SoC of the cell, SoC(t-1) as given in the equation. One option is to fully charge the cell to a known voltage. Charging to maximum cell voltage and SoC can be used as a reset and known point.

Modified Coulomb Counting method:

To improve the Coulomb counting method, a new technique called modified Coulomb counting method is proposed. The modified Coulomb counting method uses the corrected current to improve the accuracy of estimation.

The corrected current is the function of discharging current. There is a quadratic relationship between the corrected current and discharging current of battery. By practice of experimental data, corrected current is calculated by the following form:

where , k2, k1 and k0 are constant values obtained from the practice experimental data.

In modified Coulomb counting method, SOC is calculated by the following equation:

The experimental results show that the accuracy of the modified Coulomb counting method is superior to the conventional Coulomb counting method. The Coulomb counting method then calculates the remaining capacity simply by accumulating the charge transferred in or out of the battery.

 For The SOC of the battery at 2 *104second of the battery operation is checked by creating a model in simulink by using battrey,controlled current source,signal builder,bus selector & scope

The model is shown below

Aim of the project : 

In the matlab simulink connection is given below figure. The inthium-ion battery is connected to the controlled current source and signal builder.From li-ion battery terminas positive is connected to the current source of negative.negative battery terminal is connected to the output of the current souces.in the il-ion battery is terminals is one is input of current controlled soures and another one is output of current controlled sources.in below figure shown the connection.in li-ion battery capacity also wn,nominal cell voltage is 7.2 .the battery rated capacity is 1 because .in above data is battery capacity is value is the negative .The battery capacity value is negative is discharge.positive value is charge .The present value of the battery is discharge.

In the battery capacity value build the curve for build the curve we use the time and battery capacity.the value is given to single builder as per given data the curve od discharge is fomed

In the expalaination the battery is connected to the controlled current source and singular bulider.in output of the battery is charge is shown in scope.

The current is negative becuase of the battery is charging condition 

in graph is slow charging three voltage.