SOC Estimation - Results seems erroneous

[Akila1993]

Hi,

Below is a part of my code and I am in need of calculating the SOC and I'm using SoC = SoC_init - "Discharge Capacity [A.h]"/"Nominal cell capacity [A.h]" as the equation. But if you see the figure below the SOC values seems erroneous, Can someone quide me or correct me if my method is wrong. I am using Chen2020 parameter set.

#Frequencies
frequencies = np.logspace(-4, 2, 30)

# Time domain initials 
I = 1 * 1e-3
number_of_periods = 20
samples_per_period = 16

#Defining sinusoidal current function

def current_function(t):
    #return I * pybamm.sin(2 * np.pi * F * t)
    return I * pybamm.sin(2 * np.pi * pybamm.InputParameter("Frequency [Hz]") * t)

updated_parameters["Current function [A]"] = current_function

start_time = timer.time()

sim = pybamm.Simulation(model, parameter_values=updated_parameters,solver=pybamm.CasadiSolver(mode='safe without grid'),var_pts=var_pts)

#Time domain

impedances_time = []
for frequency in frequencies:
    # Solve
    period = 1 / frequency
    dt = period / samples_per_period
    t_eval = np.array(range(0, 1 + samples_per_period * number_of_periods)) * dt
    sol = sim.solve(t_eval, inputs={"Frequency [Hz]": frequency})

    # Extract final two periods of the solution
    time = sol["Time [s]"].entries[-3 * samples_per_period - 1 :]
    current = sol["Current [A]"].entries[-3 * samples_per_period - 1 :]
    voltage = sol["Terminal voltage [V]"].entries[-3 * samples_per_period - 1 :]

    # FFT
    current_fft = fft(current)
    voltage_fft = fft(voltage)

    # Get index of first harmonic
    idx = np.argmax(np.abs(current_fft))

    impedance = -voltage_fft[idx] / current_fft[idx]
    impedances_time.append(impedance)

end_time = timer.time()
time_elapsed = end_time - start_time
print("Time domain method: ", time_elapsed, "s")


#SOC estimation 

Int_SoC = 0.1;
Q = parameter_values["Nominal cell capacity [A.h]"];
solution = sim.solution
DC = solution["Discharge capacity [A.h]"]
SoC = Int_SoC-DC.entries/Q;

[valentinsulzer]

You're applying a 1 mA current to a 5 Ah battery, so I would expect the change in SOC to be very small

[Akila1993]

Thanks @tinosulzer This is the plot for 5A.

Can you please guide me on how can adjust the axis scale so that we can see the real values since you see this figure it is not properly visualizing the SOC.

[rtimms]

Your SOC is just hovering around 0.1 (see the top left, the scale is 1e-7, plus a reference value 9.9999e-2).