One way is to use conditional expressions. An example of such an expression is (a

Thank you Kimmo for your response, but where should I put this condition? If you have kind of example done by comsol using like this condition that will be great. Thanks.

You can use the parametric sweep to define the voltage range.

Thanks Ke, I think we can use the parametric sweep if I would like to supply more than one value as a ( boundary condition ) rather than one fixed value. In my problem, the output is the voltage and it is increasing with time during the charging time so I would like to stop charging once the voltage gets specific value,i.e. 2 v, then it will reverse the process to discharging with the continuing time and the output still voltage but it will be decreasing this time until getting some value,i.e. 1 v, then stop discharging and the problem is done.

Parametric sweep does not provide a solution to the original question.

I cannot give a specific answer to the question where to enter the expression as I do not know the model.

Consider for example the following. Let Vb be the battery voltage and Vc be the charging voltage. Then, (Vb

After rethinking your problem, I think that you need to implement states in your model.

For example, the system is in recharge state until the battery voltage reaches some level. Then the system enters discharge state until the battery voltage drops below some level. Then, the system enters recharge state again.

This kind of behavior can be implemented using events.

See the following blog post.

http://www.comsol.com/blogs/implementing-a-thermostat-with-the-events-interface/

Thank you Kimmo, I will look at the attached file and  I hope it finds the answer.

Best regards

I recommend contacting the technical support team @COMSOL Multiphysics to help answer any COMSOL related questions http://www.comsol.com/support. Their team of experts will guide you through the modeling process.

Thank you Fabrice for your response. I will try that.