How to fix iteration of one positive integer in an equation to update automatically in next index?

Following is the code I am using:

Batt_Power   = 45.5; % kW
Power        = 108*1000; % kW
Journery_Time_Hrs = 0.8; %hrs
Battery_Capacity = 87;    % Unit kWh Positive Intiger

Energy_Used  = cumsum(Batt_Power * ((EnergyF)/3.6/1000000))/ (Power/1000); % Cumulative Energy
Energy_Regen = FC_Charging * Journery_Time_Hrs;

% Size of Arrays
EnergyF      = 2241x1;
Energy_Used  = 1x22401;      % Unit kWh Cumulative Data
Energy_Regen = 1x22401;    % Unit kWh Cumulative Data

I am using this equation to find battery state of charge.

Soc = Battery_Capacity - Energy_Used + Energy_Regen;

% size of Soc = 1000*1

This is suppose to give me battery state of charge. However, it does not provide correct answer.

I know why but I don't know how to fix it.

The problem originates from Battery_Capacity.

Expected Correct Result:

This is the correct result I shall get if I use Soc equation correctly. The Battery Capacity must automaticaly update it self in next index of Battery_Capacity till end of the array.

87   - 0.5 + 0.3 = 86.2
86.2 - 0.7 + 0.4 = 85.9
85.9 - 1.4 + 0.5 = 85

Wrong Result From Code:

But, I am getting this kind of result, Battery_Capacity is always 87 till the end of array.

87 - 0.5 + 0.3 = 86.8
87 - 0.7 + 0.4 = 86.7
87 - 1.4 + 0.5 = 86.1

Can any one please sugguest how can I fix this.

Thanks

[James Tursa]

We would need to see your code in order to help you.

[Shahab Khan]

Ok, What part of code would you like to see.

Energy_Used = cumsum(Batt_Power * ((EnergyF)/3.6/1000000))/ (Power/1000); % Cumulative Energy
Energy_Regen = FC_Charging * Journery_Time_Hrs;

This is how I am calculating my energies. Would you like me to upload arrays?

[madhan ravi]

Man provide all the information instead of giving it bit by bit

[Shahab Khan]

@madhan ravi I have provided all the information regarding equation I am using. I am using a simulator based on hundereds of lines of code. So providing that code will be useless. All I am seeking help is about fixing the logic used in Soc equation.

[Mark Sherstan]

We need more info, for example what is the size of EnergyF? Is it a scalar or vector? Can you post a .mat file?

[KSSV]

I think after the formula for soc you need to update :

Battery_Capacity = soc ;

[Shahab Khan]

Mark Sherstan all three vectors uploaded. Size also updated in code.

Answer 1

[Cris LaPierre]

You are not updating the value of Battery_Capacity (you know that). How are you calculating SOC? All at once or inside a for loop? I think it would have to be in a loop to work because values on Soc(n+1) depend on the calculation performed in Soc(n). Taking KSSV's suggestion from above:

for idx = 1:length(Energy_Used)
    ...
    Soc(idx) = Battery_Capacity - Energy_Used(idx) + Energy_Regen(idx);
    Battery_Capacity = Soc(idx);
end

[Cris LaPierre]

Mocking up a simple example using the correct data, here's what I get:

Battery_Capacity = 87;
Energy_Used  = [0.5, 0.7, 1.4];
Energy_Regen = [0.3, 0.4, 0.5];

for idx = 1:length(Energy_Used)
    Soc(idx) = Battery_Capacity - Energy_Used(idx) + Energy_Regen(idx);
    Battery_Capacity = Soc(idx);
end

btw there is an error in your correct data set given above:

87   - 0.5 + 0.3 = 86.8 % Not 86.2
86.8 - 0.7 + 0.4 = 86.5 % Not 85.9
86.5 - 1.4 + 0.5 = 85.6 % Not 85

There is of course the goal of not using for loops. Ends up it is possible to avoid it. Since you know the incorrect value used (87), you can figure out how much each row is off and add it back in. This is quick and dirty but worked for the test data I create. I leave it to you to validate for your data:

Battery_Capacity = 87;
Soc = Battery_Capacity - Energy_Used + Energy_Regen;
val1 = [0, Soc(1:end-1) - Battery_Capacity];
val2 = cumsum(val1);
Soc = Soc + val2;

ans = 1×3    
   86.8000   86.5000   85.6000

[Cris LaPierre]

Using the variables provided in your mat file, the difference between these two approaches for calculating Soc is <1e-8

[Shahab Khan]

Cris LaPierre Thank you for your answers. I followed both of your methods and both works fine for me now. I just had to re arrange my arrays and got my desired results.

Thank you for your time.