Discussion Forum

I'm studying the Comsol manual chapter 6 : battery impedance and modeling the positive electrode's impedance nyquist plot. I have a question about optimization process that the form of optimized values change between real number and complex number. When I set the exchange current density of positive electrode i0_pos as the independent variable, I get results as complex numbers. But I get real number values when I optimize i0_pos and other variables simultaneously. When optimizing other variables except for the i0_pos individually, I could get real number values. The first picture is the result when optimizing only i0_pos and the second one is when optimizing i0_pos and cdl_pos(capacitance of positive electrode) at the same time. I think the result should be seen in the real number form regardless of variables because anyway the exchange current density is also a real number value. But the results I get make me confused. I'd like to get explicit answers. Also I tried changing optimizing method from IPOPT to BOBYQA. The problem above showed up only using the IPOPT method. I want to know the reason either.!