Calculate the SOC (State of Charge)

Hello, I would like to calculate the SoC of this battery using Q without using filters, knowing that SoC = 1 - 1/c( int of I) But I don't know where I'm going wrong, can someone help me?

[Sam Chak]

Why do you suspect that the results are incorrect? Offering additional context would enable interested users to provide potential solutions based on the information provided.

[salima chaa]

because soc should be between 0 and 1

[Sam Chak]

Hi @salima chaa,

I noticed that there are no constraints in the equation that bound the SOC response between 0 and 1. As a result, we can, in theory, conclude that the integration in Simulink is mathematically correct, even though the obtained result (Scope) may not match your expectations.

Could you please verify the differential equation once again to ensure its accuracy?

[Sam Chak]

Educated guess

Ib      = 4000;         % approximation
socODE  = @(t, x) Ib;
tspan   = [0 1.25];
x0      = 1;            % initial SOC
[t, x]  = ode45(socODE, tspan, x0);
plot(t, x, '-o'), grid on, xlabel t, ylabel SOC

Answer 1

[Sayan]

Hi salima chaa,

The SOC of the battery should remain between 0 to 1. It is hard to debug your model without the Simulink file. However, the possible reasons and their resolutions for the issue are provided below.

• In the formula for SOC calculation you provided, the term "Crated" is the full charge capacity of the battery. Ensure you have selected "Finite" for the "Battery charge capacity" parameter and configured the "Cell capacity parameter". The Constant block with the value "2.6" in your model should be replaced with the cell capacity value in Coulomb. (1 Ah = 3600 Coulomb capacity).
• If you do not need filtering in your "Derivative" block, change the value of coefficient "c" to 0 inside the block parameter.

I am attaching a sample Simulink model with a battery cell capacity of 50 Ah. It works fine for me.

You can go through the following documentation to learn more about the Battery block parameters and how to configure them.

https://www.mathworks.com/help/sps/ref/battery.html

Hope this helps in resolving the issue.