I am using the Ansys Fluent Battery Parameter Estimation tool to fit parameters to my experimental discharge curves, but all the parameters are being calculated as -1.#IND00e+00. What can be wrong?
The most common cause of this error is that the experimental discharging period is too short. This results in insufficient data to fit the curves. This can be caused unit problem or an insufficient number of experimental data points.
To have a meaningful discharge curve, the time period should cover a good portion of the DOD range. A good rule of thumb is to cover at least 80% of the depth of discharge curve at each charge rate (C-rate).
If the battery is assumed to discharge to DOD=0.2, for instance, the s sample period for C-rate=0.1 should be 0.8*3600/0.1 seconds, ..... and for C-rate=1, it should be 0.8*3600 seconds.
Note that unit of time in our tool is always in seconds, so all discharge data should obey this convention. A second source of problems might be data that is inconsistent - for instance if higher charge rates give a smaller voltage drop over the same time period at the same starting voltage.