generic battery model simulink discharge and charge more times - issue no current flow

Hi,

in advance im a newbie in matlab and simulink. i have to create a battery model for my bachelor thesis. Therefore, i have used the generic battery block out of the power systems library.

I have already created two separate models. In the first one, i am discharging the battery with a constant load. In the second one, i am charing the battery with a constant current source/voltage source. I have achieved with both models the desired values.

My next step is it to combine both models. Firstly, i want to charge the battery and afterwards to discharge again. It should be like infinite loop. Therefore, i have connected both circuits with a switch. The switch reacts when the current is less than -0.1A.

The switch is working, but here is my issue. After the battery changes from the charge to the discharge mode. The current flow goes more and more to zero, the SOC stops with a value of 92.71 and the voltage is not decreasing as well. The value with 4.13V stays slightly under the charge voltage(4.2V).

So, what i am doing wrong? Is the battery model maybe not designed for this kind of applications?

I am thankful for each kind of help.

Kind regards

Sebastian

Answer 1

[Joel Van Sickel]

Hello Sebastian,

it's hard to know without seeing your model, but I suspect that having a constant current source in your model is problematic. I would set up a more nuanced controller that uses a controlled current source if nothing else. This way you can control current flow for both charge and discharge and switch between them with simulink logic. You can base this on state of charge instead of measured current. You shouldn't use control logic based on current values when you are using controlled current sources.

Regards,

Joel