Trying to Create Pouch Cell for Experimentation

[wass-cloud]

I am trying to use pybamm to model a pouch cell and conduct experiments to accelerate the aging, however I keep getting an error for the following code. The documentation for creating unique models is limited/unclear to me, so help would be appreciated!

[wass-cloud]

The error that occurs is "builtins.KeyError: "'Battery voltage [V]' not found. Best matches are []"", and this occurs after I attempt to solve it using the Casadi solver, fast with events.

[brosaplanella]

The example works at my end, please try with the most recent PyBaMM version.

[wass-cloud]

The example previously worked for me as well, but now I'm facing errors with the casadi solver. This solver error has been occurring a lot. Found below is the error, and the code I ran was the exact same as the working example, which worked previously roughly 2 days ago. All of a sudden my code is having this type of error despite it working earlier.

The linesearch algorithm failed with too small a step.
The linesearch algorithm failed with too small a step.
The linesearch algorithm failed with too small a step.
The linesearch algorithm failed with too small a step.
The linesearch algorithm failed with too small a step.
At t = 0.808778 and h = 9.71333e-16, the corrector convergence failed repeatedly or with |h| = hmin.
2023-06-13 09:57:46.193 - [ERROR] callbacks.on_experiment_error(224): Simulation error: Maximum number of decreased steps occurred at t=0.0 (final SolverError: 'Error in Function::call for 'F' [IdasInterface] at .../casadi/core/function.cpp:1401:
Error in Function::call for 'F' [IdasInterface] at .../casadi/core/function.cpp:330:
.../casadi/interfaces/sundials/idas_interface.cpp:604: IDASolve returned "IDA_CONV_FAIL". Consult IDAS documentation.'). For a full solution try reducing dt_max (currently, dt_max=600) and/or reducing the size of the time steps or period of the experiment. Set return_solution_if_failed_early=True to return the solution object up to the point where failure occured.
Traceback (most recent call last):
File "/Users/johnlarsen/SolverIsAnnoying.py", line 20021, in
builtins.RuntimeError: Error in Function::call for 'F' [IdasInterface] at .../casadi/core/function.cpp:1401:
Error in Function::call for 'F' [IdasInterface] at .../casadi/core/function.cpp:330:
.../casadi/interfaces/sundials/idas_interface.cpp:604: IDASolve returned "IDA_CONV_FAIL". Consult IDAS documentation.

During handling of the above exception, another exception was raised:

Traceback (most recent call last):
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/pybamm/solvers/casadi_solver.py", line 250, in _integrate
current_step_sol = self._run_integrator(
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/pybamm/solvers/casadi_solver.py", line 687, in _run_integrator
raise pybamm.SolverError(error.args[0])
pybamm.expression_tree.exceptions.SolverError: Error in Function::call for 'F' [IdasInterface] at .../casadi/core/function.cpp:1401:
Error in Function::call for 'F' [IdasInterface] at .../casadi/core/function.cpp:330:
.../casadi/interfaces/sundials/idas_interface.cpp:604: IDASolve returned "IDA_CONV_FAIL". Consult IDAS documentation.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/Users/johnlarsen/SolverIsAnnoying.py", line 29, in
x = sim.solve(solver=pybamm.CasadiSolver(mode="fast with events"))
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/pybamm/simulation.py", line 786, in solve
raise error
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/pybamm/simulation.py", line 764, in solve
step_solution = solver.step(
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/pybamm/solvers/base_solver.py", line 1170, in step
solution = self._integrate(model, t_eval, model_inputs)
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/pybamm/solvers/casadi_solver.py", line 284, in _integrate
raise pybamm.SolverError(
pybamm.expression_tree.exceptions.SolverError: Maximum number of decreased steps occurred at t=0.0 (final SolverError: 'Error in Function::call for 'F' [IdasInterface] at .../casadi/core/function.cpp:1401:
Error in Function::call for 'F' [IdasInterface] at .../casadi/core/function.cpp:330:
.../casadi/interfaces/sundials/idas_interface.cpp:604: IDASolve returned "IDA_CONV_FAIL". Consult IDAS documentation.'). For a full solution try reducing dt_max (currently, dt_max=600) and/or reducing the size of the time steps or period of the experiment. Set return_solution_if_failed_early=True to return the solution object up to the point where failure occured.

[ben-kenney]

@wass-cloud Your code also doesn't work on my end. I'm on version v23.4.1.

If you change your experiment termination criteria from "Discharge at 1C for 1 hour" to something like "Discharge at 1C until 2.75V" then it works for me.

In this case I think discharging at 1C for 1hr results in a very low cell voltage that probably requires too much extrapolation somewhere in the parameter set (my first instinct would be to check the OCV curve for any extrapolation).

[brosaplanella]

@wass-cloud just checked again on my end and it works with PyBaMM 23.4.1 (most recent version). Please check that the MWE you posted above works for you (as, you didn't make inadvertent changes). If so, please share an updated MWE that shows the error.

[wass-cloud]

@brosaplanella @ben-kenney just checked again, it works when using the changes that @ben-kenney suggested. currently I am playing around with the C values since some errors arise when I change the nominal capacity to a different value, however I will look into changing the mesh to fix that. Otherwise thank you for all your help! The code is working as expected now, expect more questions from me though, pybamm seems to be a very useful and I'm excited to get used to it more and more.