Question about voltage calculation of SPMe

[Z-anti]

Hello, when I was learning the voltage calculation process using SPMe, I found that there was a difference between the voltage calculated by the formula and the voltage derived by Pybamm. What is the reason? Thank you. The following are the relevant details.

    '''
    time = solution.t
    voltage = solution["Voltage [V]"].entries
    ocp = solution["Battery open-circuit voltage [V]"].entries
    potential_concentration_pos = solution["Battery positive particle concentration overpotential [V]"].entries
    potential_concentration_neg = solution["Battery negative particle concentration overpotential [V]"].entries
    potential_reaction_neg = solution["X-averaged battery negative reaction overpotential [V]"].entries
    potential_reaction_pos = solution["X-averaged battery positive reaction overpotential [V]"].entries
    ohmic_neg = solution["X-averaged battery negative solid phase ohmic losses [V]"].entries
    ohmic_pos = solution["X-averaged battery positive solid phase ohmic losses [V]"].entries
    ohmic_electrolyte = solution["X-averaged battery electrolyte ohmic losses [V]"].entries
    ohmic_solid = -1 * (ohmic_neg - ohmic_pos)
    potential_concentration = -1 * (potential_concentration_neg - potential_concentration_pos)
    potential_reaction = -1 * (potential_reaction_neg - potential_reaction_pos)
    voltage_c = ocp + potential_concentration + potential_reaction + ohmic_solid + ohmic_electrolyte
    plt.figure(figsize=(10, 6))
    plt.plot(time, voltage, label="Measured Voltage", color="blue", linestyle="-", linewidth=2)
    plt.plot(time, voltage_c, label="Calculated Voltage", color="orange", linestyle="--", linewidth=2)
    plt.title("Voltage vs. Time", fontsize=16)
    plt.xlabel("Time [s]", fontsize=14)
    plt.ylabel("Voltage [V]", fontsize=14)
    plt.legend(fontsize=12)
    plt.grid(True)
    plt.show()
   '''

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[517623301]

I had the same problem.

[Z-anti]

In addition, when calculating the SPM, the terminal voltage calculation formula derived by pybamm is "ocp - reaction_potential - concentration_potention". How is concentration_potention calculated? The formula I saw in the Pybamm manual only includes the reaction overpotential.

[rtimms]

See #4274 and #4145