def METHOD_NAME(self):
    """Set variables relating to the state of charge."""
    # State of Charge defined as function of electrolyte concentration
    z = pybamm.standard_spatial_vars.z
    soc = (
        pybamm.Integral(
            self.variables["X-averaged electrolyte concentration [mol.m-3]"]
            / self.param.c_e_init,
            z,
        )
        * 100
    )
    self.variables.update({"State of Charge": soc, "Depth of Discharge": 100 - soc})