Regarding the current drive cycle.

[manjunathnilugal]

Hello everyone,
I am trying to run a current drive cycle, at some current values the voltage reaches maximum cut-off voltage 4.15 V. In that case I want to change the current value to "0 A" and maintain constant voltage until next discharge current value.
I am attaching the code which I am trying to execute.

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

model = pybamm.lithium_ion.SPM()
V = model.variables["Terminal voltage [V]"]

dt = 3600
time = 0
end_time = 11*3600

geometry = model.default_geometry
param = pybamm.ParameterValues("Chen2020")
#model.events.append(pybamm.Event('V', V - 4.1))

Vmin = 2.5
Vmax = 4.15

param['Lower voltage cut-off [V]'] = Vmin
param['Upper voltage cut-off [V]'] = Vmax

param['Current function [A]'] = "[input]"

param.process_model(model)
param.process_geometry(geometry)

# set mesh
mesh = pybamm.Mesh(geometry, model.default_submesh_types, model.default_var_pts)

# discretise model
disc = pybamm.Discretisation(mesh, model.default_spatial_methods)
disc.process_model(model)

I = np.array([2, 1, -2, -1, -3, -1, -2, 3, 2, 5, 4])
    
step_solver = pybamm.CasadiSolver()
step_solution = None

for i,I in enumerate(I):
    Vt = np.array([0])
    
    if  Vt[-1] >= 4.2:
        inputs = {'Current function [A]': 0.001}
    else:
        inputs = {'Current function [A]': I}
    
    step_solution = step_solver.step(step_solution, model, dt=dt, inputs=inputs, npts=100)
    V = step_solution["Terminal voltage [V]"].entries
    Vt = np.concatenate((Vt,V))
    It = step_solution["Current [A]"].entries

step_solution.plot()

I am not able to iterate the current values in the step solution, the simulation exits after the cut-off voltage is reached. Is there any method to keep the track of the voltage variation in middle of simulation ?

Instead of creating a interpolant function for current, I want to pass current individually after checking the final voltage value after each iteration.

if final voltage value is >= 4.2V:
      Current is 0.001 A
else:
      Current is [i] A

Is it possible to do using pybamm.

[TomTranter]

Does something like this work:

import pybamm
import numpy as np

model = pybamm.lithium_ion.SPM()
param = pybamm.ParameterValues("Chen2020")

drive_cycles = np.array([2, 1, -2, -1, -3, -1, -2, 3, 2, 5, 4])

Vmin = 2.5
Vmax = 4.3

param['Lower voltage cut-off [V]'] = Vmin
param['Upper voltage cut-off [V]'] = Vmax

solution = None

for i, I_app in enumerate(drive_cycles):
    if I_app < 0:
        instr = "Discharge"
        Vlim = Vmin
    else:
        instr = "Charge"
        Vlim = Vmax
    I_mag = np.abs(I_app)
    try:
        op_cond = f"{instr} at {I_mag}A for 1 hour or until {Vlim}V"
        experiment = pybamm.Experiment(operating_conditions=[op_cond])
        sim = pybamm.Simulation(model=model,
                                parameter_values=param,
                                experiment=experiment)
        solution = sim.solve(starting_solution=solution)
        time_after_solve = solution["Time [h]"].entries[-1]
    except:
        time_after_solve = i
    complete_time = i+1
    time_remaining = np.around(complete_time - time_after_solve, 5)
    if time_remaining > 0:
        print("Cycle:", i , "Hold time:", time_remaining, "hours")
        op_cond = f"Rest for {time_remaining} hours"
        op_cond = f"Hold at {Vlim}V for {time_remaining} hours"
        experiment = pybamm.Experiment(operating_conditions=[op_cond])
        sim = pybamm.Simulation(model=model,
                                parameter_values=param,
                                experiment=experiment)
        solution = sim.solve(starting_solution=solution)
sim.plot()