#492 updating current function and C-rate

examples/scripts/DFN.py

@@ -15,7 +15,7 @@
 
 # load parameter values and process model and geometry
 param = model.default_parameter_values
-param["Voltage function"] = 4.1
+param["Voltage function [V]"] = 4.1
 param.process_model(model)
 param.process_geometry(geometry)
 

examples/scripts/SPMe_SOC.py

@@ -57,7 +57,7 @@
              "Initial concentration in positive electrode [mol.m-3]": 25000,
              "Negative electrode surface area density [m-1]": 180000.0,
              "Positive electrode surface area density [m-1]": 150000.0,
-             "Typical current [A]": I_app,
+             "Current function [A]": I_app,
              }
         )
         param.process_model(model)

examples/scripts/charging_strategies.py

@@ -32,13 +32,13 @@
 params = [model.default_parameter_values for model in models]
 
 # 1. Charge at 1A
-params[0]["Typical current [A]"] = -0.1
+params[0]["Current function [A]"] = -0.1
 
 # # 2. CV: Charge at 4.1V
-params[1]["Voltage function"] = 4.1
+params[1]["Voltage function [V]"] = 4.1
 
 # 3. CP-CV: Charge at 4W
-params[2]["Power function"] = -0.4
+params[2]["Power function [W]"] = -0.4
 
 
 solutions = []

examples/scripts/compare_SPM_diffusion_models.py

@@ -23,7 +23,7 @@
 
 # load parameter values and process models and geometry
 param = models[0].default_parameter_values
-param.update({"Typical current [A]": 1})
+param.update({"Current function [A]": 1})
 for model in models:
     param.process_model(model)
 

examples/scripts/compare_comsol/compare_comsol_DFN.py

@@ -33,7 +33,7 @@
 param = pybamm_model.default_parameter_values
 param["Electrode width [m]"] = 1
 param["Electrode height [m]"] = 1
-param["Typical current [A]"] = 24 * C_rates[C_rate]
+param["Current function [A]"] = 24 * C_rates[C_rate]
 param.process_model(pybamm_model)
 param.process_geometry(geometry)
 

examples/scripts/compare_comsol/discharge_curve.py

@@ -57,7 +57,7 @@
     comsol_voltage = comsol_variables["voltage"]
 
     # update current density
-    param["Typical current [A]"] = 24 * C_rate
+    param["Current function [A]"] = 24 * C_rate
     param.update_model(model, disc)
 
     # discharge timescale

examples/scripts/compare_lead_acid.py

@@ -28,9 +28,9 @@
 param = models[0].default_parameter_values
 param.update(
     {
-        "Typical current [A]": 10,
+        "Current function [A]": 10,
         "Initial State of Charge": 1,
-        "Voltage function": 14 / 6,
+        "Voltage function [V]": 14 / 6,
     }
 )
 for model in models:

examples/scripts/compare_lead_acid_3D.py

@@ -45,7 +45,7 @@
 param = models[0].default_parameter_values
 param.update(
     {
-        "Typical current [A]": 1,
+        "Current function [A]": 1,
         "Bruggeman  coefficient": 0.001,
         "Initial State of Charge": 1,
         "Typical electrolyte concentration [mol.m-3]": 5600,

examples/scripts/compare_lithium_ion.py

@@ -26,7 +26,7 @@
 
 # load parameter values and process models and geometry
 param = models[0].default_parameter_values
-param["Typical current [A]"] = 1.0
+param["Current function [A]"] = 1.0
 
 for model in models:
     param.process_model(model)

input/parameters/lead-acid/cells/BBOXX_Sulzer2019/parameters.csv

@@ -16,3 +16,4 @@ Positive tab centre z-coordinate [m],0.114,Tab at top,
 ,,,
 # Electrical,,,
 Cell capacity [A.h],17,Manufacturer,
+Typical current [A],1,,

input/parameters/lead-acid/experiments/1C_discharge_from_full/parameters.csv

@@ -11,7 +11,6 @@ Number of cells connected in series to make a battery,6,Manufacturer,
 Lower voltage cut-off [V],1.73,,(just under) 10.5V across 6-cell battery
 Upper voltage cut-off [V],2.44,,(just over) 14.5V across 6-cell battery
 C-rate,1,,
-Current function,[constant],,
 ,,,
 # Initial conditions
 Initial State of Charge,1,-,

input/parameters/lithium-ion/cells/kokam_Marquis2019/parameters.csv

@@ -34,3 +34,4 @@ Positive current collector thermal conductivity [W.m-1.K-1],237,,
 ,,,
 # Electrical,,,
 Cell capacity [A.h],0.680616,,24 Ah/m2 * 0.137m * 0.207m
+Typical current [A],1.46925726107,,1C current

input/parameters/lithium-ion/experiments/1C_discharge_from_full_Marquis2019/parameters.csv

@@ -11,7 +11,6 @@ Number of cells connected in series to make a battery,1,,
 Lower voltage cut-off [V],3.105,,
 Upper voltage cut-off [V],4.7,,
 C-rate,1,,
-Current function,[constant],,
 ,,,
 # Initial conditions
 Initial concentration in negative electrode [mol.m-3],19986.609595075,Scott Moura FastDFN,

pybamm/models/submodels/external_circuit/base_external_circuit.py

@@ -10,6 +10,20 @@ class BaseModel(pybamm.BaseSubModel):
     def __init__(self, param):
         super().__init__(param)
 
+    def _get_current_variables(self, i_cell):
+        param = self.param
+        I = i_cell * abs(param.I_typ)
+        i_cell_dim = I / (param.n_electrodes_parallel * param.A_cc)
+
+        variables = {
+            "Total current density": i_cell,
+            "Total current density [A.m-2]": i_cell_dim,
+            "Current [A]": I,
+            "C-rate": I / param.Q,
+        }
+
+        return variables
+
     def get_fundamental_variables(self):
         Q = pybamm.Variable("Discharge capacity [A.h]")
         variables = {"Discharge capacity [A.h]": Q}

pybamm/models/submodels/external_circuit/current_control_external_circuit.py

@@ -21,6 +21,7 @@ def get_fundamental_variables(self):
             "Total current density": i_cell,
             "Total current density [A.m-2]": i_cell_dim,
             "Current [A]": I,
+            "C-rate": I / self.param.Q,
         }
 
         # Add discharge capacity variable

pybamm/models/submodels/external_circuit/function_control_external_circuit.py

@@ -14,16 +14,8 @@ def __init__(self, param, external_circuit_class):
 
     def get_fundamental_variables(self):
         # Current is a variable
-        param = self.param
         i_cell = pybamm.Variable("Total current density")
-        I = i_cell * abs(param.I_typ)
-        i_cell_dim = I / (param.n_electrodes_parallel * param.A_cc)
-
-        variables = {
-            "Total current density": i_cell,
-            "Total current density [A.m-2]": i_cell_dim,
-            "Current [A]": I,
-        }
+        variables = self._get_current_variables(i_cell)
 
         # Add discharge capacity variable
         variables.update(super().get_fundamental_variables())
@@ -78,7 +70,7 @@ class ConstantVoltage:
 
     def __call__(self, variables):
         V = variables["Terminal voltage [V]"]
-        return V - pybamm.FunctionParameter("Voltage function", pybamm.t)
+        return V - pybamm.FunctionParameter("Voltage function [V]", pybamm.t)
 
 
 class PowerFunctionControl(FunctionControl):
@@ -94,5 +86,5 @@ class ConstantPower:
     def __call__(self, variables):
         I = variables["Current [A]"]
         V = variables["Terminal voltage [V]"]
-        return I * V - pybamm.FunctionParameter("Power function", pybamm.t)
+        return I * V - pybamm.FunctionParameter("Power function [W]", pybamm.t)
 

pybamm/models/submodels/external_circuit/voltage_control_external_circuit.py

@@ -15,7 +15,7 @@ def __init__(self, param):
 
     def get_fundamental_variables(self):
         # Voltage is given as a function of time
-        V_dim = pybamm.FunctionParameter("Voltage function", pybamm.t)
+        V_dim = pybamm.FunctionParameter("Voltage function [V]", pybamm.t)
 
         param = self.param
         V = (V_dim - (param.U_p_ref - param.U_n_ref)) / param.potential_scale
@@ -37,13 +37,6 @@ def get_coupled_variables(self, variables):
             param.sigma_p * tor, "right"
         ) * pybamm.BoundaryGradient(phi_s_p, "right")
         i_cell = pybamm.BoundaryValue(i_boundary_cc, "positive tab")
-        I = i_cell * abs(param.I_typ)
-        i_cell_dim = I / (param.n_electrodes_parallel * param.A_cc)
-
-        variables = {
-            "Total current density": i_cell,
-            "Total current density [A.m-2]": i_cell_dim,
-            "Current [A]": I,
-        }
+        variables = self._get_current_variables(i_cell)
 
         return variables

pybamm/parameters/electrical_parameters.py

@@ -25,7 +25,7 @@
 # the user may provide the typical timescale as a parameter.
 timescale = pybamm.Parameter("Typical timescale [s]")
 dimensional_current_with_time = pybamm.FunctionParameter(
-    "Current function", pybamm.t * timescale
+    "Current function [A]", pybamm.t * timescale
 )
 dimensional_current_density_with_time = dimensional_current_with_time / (
     n_electrodes_parallel * pybamm.geometric_parameters.A_cc

pybamm/parameters/parameter_values.py

@@ -178,9 +178,6 @@ def update(self, values, check_conflict=False, path=""):
                         ).to_numpy()
                         # Save name and data
                         super().__setitem__(name, (function_name, data))
-                    # Special case (hacky) for zero current
-                    elif value == "[zero]":
-                        super().__setitem__(name, 0)
                     # Anything else should be a converted to a float
                     else:
                         super().__setitem__(name, float(value))
@@ -190,19 +187,18 @@ def update(self, values, check_conflict=False, path=""):
         self._processed_symbols = {}
 
     def check_and_update_parameter_values(self, values):
-        # Make sure "C-rate" and current are both non-zero
-        if "C-rate" in values and values["C-rate"] == 0:
+        # Make typical current is non-zero
+        if "Typical current [A]" in values and values["Typical current [A]"] == 0:
             raise ValueError(
                 """
-                "C-rate" cannot be zero. A possible alternative is to set
-                "Current function" to `0` instead.
+                "Typical current [A]" cannot be zero. A possible alternative is to set
+                "Current function [A]" to `0` instead.
                 """
             )
-        if "Typical current [A]" in values and values["Typical current [A]"] == 0:
+        if "C-rate" in values and "Current function [A]" in values:
             raise ValueError(
                 """
-                "Typical current [A]" cannot be zero. A possible alternative is to set
-                "Current function" to `0` instead.
+                Cannot provide both "C-rate" and "Current function [A]" simultaneously
                 """
             )
         # If the capacity of the cell has been provided, make sure "C-rate" and current
@@ -214,30 +210,22 @@ def check_and_update_parameter_values(self, values):
             else:
                 capacity = self["Cell capacity [A.h]"]
             # Make sure they match if both provided
-            if "C-rate" in values and "Typical current [A]" in values:
-                if values["C-rate"] * capacity != values["Typical current [A]"]:
-                    raise ValueError(
-                        """
-                        "C-rate" ({}C) and Typical current ({} A) provided do not match
-                        given capacity ({} Ah). These can be updated individually
-                        instead.
-                        """.format(
-                            values["C-rate"], values["Typical current [A]"], capacity
-                        )
-                    )
             # Update the other if only one provided
-            elif "C-rate" in values:
-                values["Typical current [A]"] = float(values["C-rate"]) * capacity
-            elif "Typical current [A]" in values:
-                values["C-rate"] = float(values["Typical current [A]"]) / capacity
-
-        # Update the current function if it is constant
-        self_and_values = {**self, **values}
-        if "Current function" in self_and_values and (
-            self_and_values["Current function"] == "[constant]"
-            or isinstance(self_and_values["Current function"], numbers.Number)
-        ):
-            values["Current function"] = {**self, **values}["Typical current [A]"]
+            if "C-rate" in values:
+                # Can't provide C-rate as a function
+                if callable(values["C-rate"]):
+                    values["Current function [A]"] = CrateToCurrent(
+                        values["C-rate"], capacity
+                    )
+                else:
+                    values["Current function [A]"] = float(values["C-rate"]) * capacity
+            elif "Current function [A]" in values:
+                if callable(values["Current function [A]"]):
+                    values["C-rate"] = CurrentToCrate(
+                        values["Current function [A]"], capacity
+                    )
+                else:
+                    values["C-rate"] = float(values["Current function [A]"]) / capacity
 
         return values
 
@@ -546,3 +534,23 @@ def evaluate(self, symbol):
             return processed_symbol.evaluate()
         else:
             raise ValueError("symbol must evaluate to a constant scalar")
+
+
+class CurrentToCrate:
+    "Convert a current function to a C-rate function"
+    def __init__(self, function, capacity):
+        self.function = function
+        self.capacity = capacity
+
+    def __call__(self, t):
+        return self.function(t) / self.capacity
+
+
+class CrateToCurrent:
+    "Convert a C-rate function to a current function"
+    def __init__(self, function, capacity):
+        self.function = function
+        self.capacity = capacity
+
+    def __call__(self, t):
+        return self.function(t) * self.capacity

pybamm/parameters/standard_parameters_lead_acid.py

@@ -487,7 +487,7 @@ def U_p(c_e_p, T):
 # 6. Input current and voltage
 
 dimensional_current_with_time = pybamm.FunctionParameter(
-    "Current function", pybamm.t * timescale
+    "Current function [A]", pybamm.t * timescale
 )
 dimensional_current_density_with_time = dimensional_current_with_time / (
     n_electrodes_parallel * pybamm.geometric_parameters.A_cc

pybamm/parameters/standard_parameters_lithium_ion.py

@@ -443,7 +443,7 @@ def dUdT_p(c_s_p):
 # 6. Input current and voltage
 
 dimensional_current_with_time = pybamm.FunctionParameter(
-    "Current function", pybamm.t * timescale
+    "Current function [A]", pybamm.t * timescale
 )
 dimensional_current_density_with_time = dimensional_current_with_time / (
     n_electrodes_parallel * pybamm.geometric_parameters.A_cc

results/2019_08_sulzer_thesis/self_discharge.py

@@ -31,9 +31,7 @@ def self_discharge_states(compute):
                 name="LOQS, with oxygen",
             ),
         ]
-        extra_parameter_values = {
-            "Current function": "[zero]"
-        }
+        extra_parameter_values = {"Current function [A]": 0}
         t_eval = np.linspace(0, 1000, 100)
         all_variables, t_eval = model_comparison(
             models, [1], t_eval, extra_parameter_values=extra_parameter_values

results/2019_08_sulzer_thesis/shared_solutions.py

@@ -36,7 +36,7 @@ def model_comparison(models, Crates, t_eval, extra_parameter_values=None):
         all_variables[Crate] = {}
         current = Crate * 17
         pybamm.logger.info("Setting typical current to {} A".format(current))
-        param.update({"Typical current [A]": current})
+        param.update({"Current function [A]": current})
         for model in models:
             param.update_model(model, discs[model])
             solution = model.default_solver.solve(model, t_eval)
@@ -86,7 +86,7 @@ def convergence_study(models, Crates, all_npts, t_eval, extra_parameter_values=N
         for Crate in Crates:
             current = Crate * 17
             pybamm.logger.info("Setting typical current to {} A".format(current))
-            param.update({"Typical current [A]": current})
+            param.update({"Current function [A]": current})
             for model in models:
                 model_disc = models_disc[model.name]
                 disc = discs[model.name]

results/2plus1D/spm_1plus1D.py

@@ -22,7 +22,7 @@
 current_1C = 24 * param.process_symbol(pybamm.geometric_parameters.A_cc).evaluate()
 param.update(
     {
-        "Typical current [A]": C_rate * current_1C,
+        "Current function [A]": C_rate * current_1C,
         "Initial temperature [K]": 298.15,
         "Negative current collector conductivity [S.m-1]": 1e7,
         "Positive current collector conductivity [S.m-1]": 1e7,

results/2plus1D/user_mesh_spm_1plus1D.py

@@ -22,7 +22,7 @@
 current_1C = 24 * param.evaluate(pybamm.geometric_parameters.A_cc)
 param.update(
     {
-        "Typical current [A]": C_rate * current_1C,
+        "Current function [A]": C_rate * current_1C,
         "Initial temperature [K]": 298.15,
         "Negative current collector conductivity [S.m-1]": 1e5,
         "Positive current collector conductivity [S.m-1]": 1e5,

results/drive_cycles/US06_simulation.py

@@ -13,7 +13,7 @@
 
 # load parameter values and process model and geometry
 param = model.default_parameter_values
-param["Current function"] = "[current data]US06"
+param["Current function [A]"] = "[current data]US06"
 param.process_model(model)
 param.process_geometry(geometry)