diff --git a/src/pybamm/models/full_battery_models/lithium_ion/electrode_soh_half_cell.py b/src/pybamm/models/full_battery_models/lithium_ion/electrode_soh_half_cell.py
index fb0ee6715e..012169ef00 100644
--- a/src/pybamm/models/full_battery_models/lithium_ion/electrode_soh_half_cell.py
+++ b/src/pybamm/models/full_battery_models/lithium_ion/electrode_soh_half_cell.py
@@ -31,7 +31,7 @@ def __init__(self, name="ElectrodeSOH model"):
         Q_w = pybamm.InputParameter("Q_w")
         T_ref = param.T_ref
         U_w = param.p.prim.U
-        Q = Q_w * (x_100 - x_0)
+        Q = Q_w * (x_0 - x_100)
 
         V_max = param.ocp_soc_100
         V_min = param.ocp_soc_0
@@ -49,13 +49,12 @@ def __init__(self, name="ElectrodeSOH model"):
             "Uw(x_100)": U_w(x_100, T_ref),
             "Uw(x_0)": U_w(x_0, T_ref),
             "Q_w": Q_w,
-            "Q_w * (x_100 - x_0)": Q_w * (x_100 - x_0),
         }
 
     @property
     def default_solver(self):
         # Use AlgebraicSolver as CasadiAlgebraicSolver gives unnecessary warnings
-        return pybamm.AlgebraicSolver()
+        return pybamm.AlgebraicSolver(method="minimize  L-BFGS-B", tol=1e-7)
 
 
 def get_initial_stoichiometry_half_cell(