#923 fix composite extended model

examples/scripts/compare_lead_acid.py

@@ -19,13 +19,13 @@
 models = [
     pybamm.lead_acid.LOQS(),
     pybamm.lead_acid.FOQS(),
-    pybamm.lead_acid.Composite(),
+    pybamm.lead_acid.CompositeExtended(),
     pybamm.lead_acid.Full(),
 ]
 
 # load parameter values and process models and geometry
 param = models[0].default_parameter_values
-param.update({"Current function [A]": 10, "Initial State of Charge": 1})
+param.update({"Current function [A]": 85, "Initial State of Charge": 1})
 for model in models:
     param.process_model(model)
 

pybamm/models/submodels/electrolyte_diffusion/composite_diffusion.py

@@ -92,11 +92,17 @@ def _get_source_terms_leading_order(self, variables):
         )
 
     def _get_source_terms_first_order(self, variables):
+        param = self.param
+        c_e_n = variables["Negative electrolyte concentration"]
+        c_e_p = variables["Positive electrolyte concentration"]
+
         return sum(
             pybamm.Concatenation(
-                reaction["Negative"]["s"] * variables[reaction["Negative"]["aj"]],
+                (reaction["Negative"]["s"] - param.t_plus(c_e_n))
+                * variables[reaction["Negative"]["aj"]],
                 pybamm.FullBroadcast(0, "separator", "current collector"),
-                reaction["Positive"]["s"] * variables[reaction["Positive"]["aj"]],
+                (reaction["Positive"]["s"] - param.t_plus(c_e_p))
+                * variables[reaction["Positive"]["aj"]],
             )
             / self.param.gamma_e
             for reaction in self.reactions.values()