Add standard variables to Thevenin() class

CHANGELOG.md

@@ -8,6 +8,7 @@
 
 - Parameters in `Prada2013` have been updated to better match those given in the paper, which is a 2.3 Ah cell, instead of the mix-and-match with the 1.1 Ah cell from Lain2019.
 - Error generated when invalid parameter values are passed.
+- Thevenin() model is now constructed with standard variables: `Time [s], Time [min], Time [h]` ([#3143](https://github.com/pybamm-team/PyBaMM/pull/3143)) 
 
 # [v23.5](https://github.com/pybamm-team/PyBaMM/tree/v23.5) - 2023-06-18
 

pybamm/models/full_battery_models/equivalent_circuit/thevenin.py

@@ -68,6 +68,7 @@ def __init__(
         self.param = pybamm.EcmParameters()
         self.element_counter = 0
 
+        self.set_standard_output_variables()
         self.set_submodels(build)
 
     def set_options(self, extra_options=None):
@@ -192,6 +193,16 @@ def set_submodels(self, build):
         if build:
             self.build_model()
 
+    def set_standard_output_variables(self):
+        # Time
+        self.variables.update(
+            {
+                "Time [s]": pybamm.t,
+                "Time [min]": pybamm.t / 60,
+                "Time [h]": pybamm.t / 3600,
+            }
+        )
+
     def build_model(self):
         # Build model variables and equations
         self._build_model()