Simulation error while setting temperatures for different battery cells

[Yang-Qirui]

I am currently trying to simulate a battery pack failure by inducing abnormal temperatures in certain batteries within the battery pack. However, when I follow the guidance to set the 'Ambient Temperature', the simulation cannot be conducted due to the error Low voltage limit reached. And when I try to set the 'Initial Temperature', the error RuntimeError: .../casadi/core/function_internal.hpp:1257: Input 2 (i2) has mismatching shape. Got 2-by-1. will occur.

Below is my python code:

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

I_mag = 5.0
OCV_init = 4.0  # used for intial guess
Ri_init = 5e-2  # used for intial guess
R_busbar = 1.5e-3
R_connection = 1e-2
Np = 4
Ns = 1
Nbatt = Np * Ns
netlist = lp.setup_circuit(
    Np=Np, Ns=Ns, Rb=R_busbar, Rc=R_connection, Ri=Ri_init, V=OCV_init, I=I_mag
)

print(netlist)

experiment = pybamm.Experiment(
    [
        "Charge at 5 A for 30 minutes",
        "Rest for 15 minutes",
        "Discharge at 5 A for 30 minutes",
        "Rest for 15 minutes",
    ],
    period="10 seconds",
)

parameter_values = pybamm.ParameterValues("Chen2020")
temperature_input = {"Ambient temperature [K]": np.array([1,1,1.1,1]) * 298.15} 
parameter_values.update({"Ambient temperature [K]":"[input]"})
# temperature_input = {"Initial temperature [K]": np.array([1,1,1.1,1]) * 298.15} 
# parameter_values.update({"Initial temperature [K]":"[input]"})
SPMe = pybamm.models.full_battery_models.lithium_ion.SPMe()
output_variables = [
    "Battery voltage [V]",
    "Current [A]",
]

output = lp.solve(
    netlist=netlist,
    parameter_values=parameter_values,
    experiment=experiment,
    output_variables=output_variables,
    initial_soc=0.5,
    inputs=temperature_input
)

lp.plot_output(output)

Does any one know what should I do? Any support will be appreciated.

[MustafaDragonborne]

Can you try replacing the "input" in parameter_values.update({"Ambient temperature [K]":"[input]"}) with "temperature_input" ?

[Yang-Qirui]

Thanks for reply! However the program still throws an error "ValueError: could not convert string to float: '[temperature_input]'".

[TomTranter]

I think there might actually be a bug with the order of the inputs assumed by the solver when specifying "Ambient temperature" as input as this should work but it doesn't. In the mean-time I think I have a work-around which is to define a sim_func and specify a single "Input Temperature" for ambient and initial.

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


def thermal_external(parameter_values=None):
    """
    Create a PyBaMM simulation set up for integration with liionpack.
    External thermal option is used so that temperature dependence can be
    included in models but temperature supplied by another algorithm. This
    is useful for packs and cells where thermal connections are seperate or
    distinct from electrical connections.

    Args:
        parameter_values (pybamm.ParameterValues):
            The default is None.

    Returns:
        pybamm.Simulation:
            A simulation that can be solved individually or passed into the
            liionpack solve method

    """
    # Create the pybamm model
    model = pybamm.lithium_ion.SPMe(
        options={
            "calculate heat source for isothermal models": "true",
            "cell geometry": "arbitrary",
            "dimensionality": 0,
            "thermal": "lumped",
        }
    )

    # Add events to the model
    model = lp.add_events_to_model(model)

    # Set up parameter values
    if parameter_values is None:
        parameter_values = pybamm.ParameterValues("Chen2020")

    # Change the ambient temperature to be an input controlled by the
    # external circuit
    parameter_values["Ambient temperature [K]"] = pybamm.InputParameter(
        "Input temperature [K]"
    )
    parameter_values["Initial temperature [K]"] = pybamm.InputParameter(
        "Input temperature [K]"
    )

    # Set up solver and simulation
    solver = pybamm.CasadiSolver(mode="safe")
    sim = pybamm.Simulation(
        model=model,
        parameter_values=parameter_values,
        solver=solver,
    )
    return sim


I_mag = 5.0
OCV_init = 4.0  # used for intial guess
Ri_init = 5e-2  # used for intial guess
R_busbar = 1.5e-3
R_connection = 1e-2
Np = 4
Ns = 1
Nbatt = Np * Ns
netlist = lp.setup_circuit(
    Np=Np, Ns=Ns, Rb=R_busbar, Rc=R_connection, Ri=Ri_init, V=OCV_init, I=I_mag
)

print(netlist)

experiment = pybamm.Experiment(
    [
        "Charge at 5 A for 30 minutes",
        "Rest for 15 minutes",
        "Discharge at 5 A for 30 minutes",
        "Rest for 15 minutes",
    ],
    period="10 seconds",
)

parameter_values = pybamm.ParameterValues("Chen2020")
T_amb = np.array([1,1,1.1,1]) * 298.15
temperature_input = {
    "Input temperature [K]": T_amb,
    } 

output_variables = [
    "Battery voltage [V]",
    "Current [A]",
    "Ambient temperature [K]",
    "Volume-averaged cell temperature [K]"
]

output = lp.solve(
    netlist=netlist,
    sim_func=thermal_external,
    parameter_values=parameter_values,
    experiment=experiment,
    output_variables=output_variables,
    initial_soc=0.5,
    inputs=temperature_input
)

lp.plot_output(output)

[Yang-Qirui]

Thanks for your reply! I'll try later. Actually I found if set Ambient Temperature in external_variables, it works fine. But will still face the problem of setting Intial Temperature. Btw, I'm wondering if there's any method to get data like discharge capacity? I remember pybamm has a summary_variables property in Simulation.Solution, but I'm not sure if liionpack has the same.

[TomTranter]

No that would have to be added as a new feature. It's on our roadmap to standardize the PyBaMM and liionpack solving and experiments in the near future so that should be included

[Yang-Qirui]

Got it. So is there any existing method to get properties like discharge capacity?