Problems with current function and initial_soc using Ai2020 parameter set.

[HassanSewailem]

Hello,

I am currently trying to simulate charging a battery using a constant current of -2.28 A (1C). However, when I set the current function to any -ve value, the solver crashes giving the error "psetup failed: .../casadi/interfaces/sundials/idas_interface.cpp:852: Linear solve failed
".
I thought this error arose because the base settings for the battery that it is fully charged, so I tried changing the 'initial_soc' in the solve to be for example 0.5, then I encountered another error being "SolverError: Could not find acceptable solution: solver terminated successfully, but maximum solution error (4.200000000000051) above tolerance (1e-06)".

Any ideas on how fix such a problem? The code can be found below.

import pybamm
import numpy as np
import matplotlib.pyplot as plt

dfn = pybamm.lithium_ion.DFN()
chemistry = pybamm.parameter_sets.Ai2020
params = pybamm.ParameterValues(chemistry=chemistry)
params['Current function [A]'] = -2.28

sim = pybamm.Simulation(dfn, parameter_values=params)
solution = sim.solve(t_eval =[0, 3600], initial_soc = 0.5)
sim.plot()

[rtimms]

It seems to be a problem with the solver using to find the initial conditions. A workaround for now is to discharge and then set the initial conditions based on that solution, e.g. something like

import pybamm

model = pybamm.lithium_ion.DFN()
params = pybamm.ParameterValues("Ai2020")

discharge_exp = pybamm.Experiment(["Discharge at C/10 until 3V"])
discharge_sim = pybamm.Simulation(model, parameter_values=params, experiment=discharge_exp)
discharge_sol = discharge_sim.solve(calc_esoh=False)

# MODEL RE-INITIALIZATION: #############################################################
# Now initialize the model with the solution of the discharge, and then charge 
# We could also do this inplace by setting inplace to True, which modifies the original
# model in place
new_model = model.set_initial_conditions_from(discharge_sol, inplace=False)
########################################################################################

charge_exp = pybamm.Experiment(["Charge at 1C until 4.2V"])
charge_sim = pybamm.Simulation(new_model, parameter_values=params, experiment=charge_exp)
charge_sol = charge_sim.solve(calc_esoh=False)
charge_sol.plot()