I am trying to implement a constant-current constant-voltage charging strategy using the COMSOL standard lithium-ion battery model that comes with the chemical engineering module.
The idea is to apply a constant current to the cell until the voltage reaches some limit; after that point, apply constant voltage to the cell until cell current drops below some value. For the first segment of time, current is constrained and voltage is unconstrained. For the second segment of time, terminal voltage is constrained and current is unconstrained.
Does anyone know how to switch this boundary condition -- mid simulation -- to perform this operation?
Thanks.
Hi, Nikolaos,
I can help you but first, I need to know what version of Comsol do you use?
Regards,
Bence
Hi,
I am using Comsol v5.1 and v5.3 but I think basically 2 main concept can be followed to implement charge/discharge functions.
1.) You can set a step function in e.g. global definition and set step time (X can be considered as time variable now) where you want to change from discharge to charge. Then, you should define i applied current with logical relationship to step function. These together defines when the discharging and charging should be applied respect to time-frame. So, you should have:
- i_app as applied current that defines the amplitude of cell current
- 2 logical values related to the step function that set the time when you want to switch
It requires to set the initial values for positive and negative electrode and electrolyte properly, for example, at fully charged state (SOC=1).
It basically implements CV mode with current limit.
2.) In v5.3 there is a boundary condition called charge-discharge cycling under the Li-ion physics in the Electrode subnode. This is the fastest and easiest way if you could have access to that software. That implements CC and CV mode too.
I have attached some pics from settings in v5.1 for guide.
I could send you a template if you installed Comsol v5.1 or v5.3.
Regards,
Bence
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