Error in defining custom experiment.

[kumaryash7]

I am trying to define a custom experiment where I am trying to use Discharge capacity as a termination condition for my experiment.
The part of my code implementing this is : -

import pybamm

model = pybamm.lithium_ion.DFN()

model.variables["Capac [A.h]"] = model.variables['Discharge capacity [A.h]']
parameter_values = pybamm.ParameterValues("Prada2013")

def cap_cutoff(variables):
return variables["Capac [A.h]"] - 0.46

The CustomTermination class takes a name and function

cap_termination = pybamm.step.CustomTermination(
name="Capacity cut-off [A.h]", event_function=cap_cutoff
)

Provide a list of termination events, each step will stop whenever the first

termination event is reached

terminations = [cap_termination]
experiment = pybamm.Experiment(
[
(
pybamm.step.c_rate(1, termination=terminations),

        "Discharge at 1 C until 2V"

​
)

]

)

sim = pybamm.Simulation(model, parameter_values=parameter_values, experiment=experiment)
​
sim.solve(initial_soc=1)

This is giving error as : -
ModelError:
No key set for variable 'Discharge capacity [A.h]'. Make sure it is included in either
model.rhs or model.algebraic in an unmodified form
(e.g. not Broadcasted).

[valentinsulzer]

This is a bug, it's fixed in develop #4018
Will be fixed in next release.
For now if you add another variable model.variables["double capacity"] = 2 * model.variables["Discharge capacity [A.h]"] it should work

[kumaryash7]

I tried adding this, but an error comes up. I am trying to keep a termination condition of discharge capacity on my discharge curve.
This is the code.

import pybamm

Set up model and parameters

model = pybamm.lithium_ion.DFN()

sorted(model.variables.keys())

model.variable_names()

model.variables["Capac [A.h]"] = model.variables['Discharge capacity [A.h]']
parameter_values = pybamm.ParameterValues("Prada2013")
model.variables["double capacity"] = 2 * model.variables["Discharge capacity [A.h]"]

def cap_cutoff(variables):
return variables["Capac [A.h]"] - 1

The CustomTermination class takes a name and function

cap_termination = pybamm.step.CustomTermination(
name="Capacity cut-off [A.h]", event_function=cap_cutoff
)

Provide a list of termination events, each step will stop whenever the first

termination event is reached

terminations = [cap_termination]
​
experiment = pybamm.Experiment(
[
(
pybamm.step.c_rate(1, termination=terminations),

    )
    
]
*1

)
1

Set up simulation

sim = pybamm.Simulation(model, parameter_values=parameter_values, experiment=experiment)
​
sim.solve(initial_soc=1)

SolverError Traceback (most recent call last)
Cell In[102], line 4
1 # Set up simulation
2 sim = pybamm.Simulation(model, parameter_values=parameter_values, experiment=experiment)
----> 4 sim.solve(initial_soc=1)

File ~/anaconda3/lib/python3.11/site-packages/pybamm/simulation.py:882, in Simulation.solve(self, t_eval, solver, check_model, save_at_cycles, calc_esoh, starting_solution, initial_soc, callbacks, showprogress, **kwargs)
880 if all(isinstance(step, pybamm.EmptySolution) for step in steps):
881 if len(steps) == 1:
--> 882 raise pybamm.SolverError(
883 f"Step '{op_conds_str}' is infeasible "
884 "due to exceeded bounds at initial conditions. "
885 "If this step is part of a longer cycle, "
886 "round brackets should be used to indicate this, "
887 "e.g.:\n pybamm.Experiment([(\n"
888 "\tDischarge at C/5 for 10 hours or until 3.3 V,\n"
889 "\tCharge at 1 A until 4.1 V,\n"
890 "\tHold at 4.1 V until 10 mA\n"
891 "])"
892 )
893 else:
894 this_cycle = self.experiment.operating_conditions_cycles[
895 cycle_num - 1
896 ]

SolverError: Step '_Step(C-rate, 1, termination=[<pybamm.experiment.step.step_termination.CustomTermination object at 0x179cee510>])' is infeasible due to exceeded bounds at initial conditions. If this step is part of a longer cycle, round brackets should be used to indicate this, e.g.:
pybamm.Experiment([(
Discharge at C/5 for 10 hours or until 3.3 V,
Charge at 1 A until 4.1 V,
Hold at 4.1 V until 10 mA
])

[Thiyaga2025]

@kumaryash7 ,

I am trying similar thing with no success. are you able to overcome this error. will appreciate any help here.

regards