team pybamm,
I am modeling discharge/charge behavior of an NMC cell and have issues with modeling voltage recovery. In the test, after discharging at C/5(constant current), there is a rest period of 60 minutes and the voltage recovers steadily throughout the rest period of 60 minutes. But in pybamm model i just see a recovery for few seconds and the voltage curve remains flat for the remaining rest period(current is zero). How can I improve my model prediction. I am using DFN model and played around with contact resistance but it did not help much. what is lacking in my pybamm model. please help me here. attached is the voltage(primary axis)/current(secondary axis) plot.
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Hi, I’m having the same issue. From what I saw in the documentation the MP-DFN model should behave better for the voltage relaxation region. But I encountered an issue so I’ll just ask this as an extension of your question to not overcrowd. My simulation won’t work when I use the MP-DFN with the standard pybamm.Experiment class with a RPT sequence almost as identical as the one shown above. PyBaMM is passing discretisation and simulation errors along with:
UnboundLocalError: cannot access local variable ‘matrix’ where it is not associated with a value.
I’m not sure how to fix this so I would appreciate a bit of guidance. I’m currently using PyBaMM 24.1. Thanks in advance to whoever has any type of help for both of us 
I’m linking the MP-DFN page here: Doyle-Fuller-Newman Model with particle-size distributions — PyBaMM v25.10.2 Manual
Also the research paper from Kirk et al. is quite a nice read on this theme so I’m linking it as well (even though it is in the citations portion on the MP-DFN page):
Toby L. Kirk, Colin P. Please, and S. Jon Chapman. Physical modelling of the slow voltage relaxation phenomenon in lithium-ion batteries. Journal of The Electrochemical Society, 168(6):060554, jun 2021. URL: Radware Bot Manager Captcha , doi:10.1149/1945-7111/ac0bf7.
Just to add, I think that if you play with diffusion parameters it can help a bit. I’ve found that modifying the positive electrode diffusivity parameters helps to minimize the discrepancy that you have here. That should be a much easier mod than switching to a MP-DFN.
Also, I’m not an expert in electrochemical engineering, I’m an electrical engineer but have experience in battery modeling, so take my comments with a grain of salt, and I hope they help just a little bit until we hear from someone on the PyBaMM team.
Cheers
