Saving data to file

[zeecode07]

when I save cccv to csv with multiple cycles, I get an error like this


can you describe the correct syntax for saving to csv? @tinosulzer

[brosaplanella]

Seems an issue with the size of the variables your are trying to save. I would guess it's the temperature, but hard to tell without knowing which model you are solving.

[zeecode07]

i used model SPM

[brosaplanella]

Please share a minimum working example so we can see the whole settings.

[zeecode07]

here is my code @brosaplanella

options={
    "SEI":"reaction limited",
    "SEI on cracks": "true",
   }
parameter_values = pybamm.ParameterValues("OKane2022")
model = pybamm.lithium_ion.SPM(options = options)
# Calculate stoichiometries at 100% SOC
parameter_values.set_initial_stoichiometries(1);
var_pts = {"x_n": 7, "x_s": 7, "x_p": 7, "r_n": 20, "r_p": 20}
pybamm.set_logging_level("NOTICE")

experiment = pybamm.Experiment([
    ("Discharge at 0.1C until 2.5V",
     "Rest for 1 hour",
     "Charge at 0.1C until 4.2V", 
     "Hold at 4.2V until C/50")
])
sim = pybamm.Simulation(model, experiment=experiment, parameter_values=parameter_values, var_pts=var_pts)
sol = sim.solve()
sol.plot(["Current [A]", "Voltage [V]"])
# We can only save 0D variables to csv
sim.solution.save_data(
    "out_01.csv",
    [
        "Time [h]",
        "Current [A]",
        "Voltage [V]",
        "Discharge capacity [A.h]",
        "X-averaged cell temperature [K]",
    ],
    to_format="csv",
)

experiment = pybamm.Experiment([
    ("Discharge at 0.1C until 2.5V",
     "Rest for 1 hour",
     "Charge at 0.1C until 4.2V", 
     "Hold at 4.2V until C/50")
] * 5000,
termination="80% capacity")

sim = pybamm.Simulation(model, experiment=experiment, parameter_values=parameter_values, var_pts=var_pts)
sol = sim.solve()

sim.solution.save_data(
    "out_1(2).csv",
    [
        "Time [h]",
        "Current [A]",
        "Voltage [V]",
        "Discharge capacity [A.h]",
        "X-averaged cell temperature [K]",
    ],
    to_format="csv",
)

got an error when saving many cycles

ValueError                                Traceback (most recent call last)
Cell In[11], line 2
      1 # We can only save 0D variables to csv
----> 2 sim.solution.save_data(
      3     "out_1(2).csv",
      4     [
      5         "Time [h]",
      6         "Current [A]",
      7         "Voltage [V]",
      8         "Discharge capacity [A.h]",
      9         "X-averaged cell temperature [K]",
     10     ],
     11     to_format="csv",
     12 )

File [E:\ANACONDA\lib\site-packages\pybamm\solvers\solution.py:677](file:///E:/ANACONDA/lib/site-packages/pybamm/solvers/solution.py:677), in Solution.save_data(self, filename, variables, to_format, short_names)
    671         if var.ndim >= 2:
    672             raise ValueError(
    673                 "only 0D variables can be saved to csv, but '{}' is {}D".format(
    674                     name, var.ndim - 1
    675                 )
    676             )
--> 677     df = pd.DataFrame(data)
    678     return df.to_csv(filename, index=False)
...
    669     raise ValueError(
    670         "Mixing dicts with non-Series may lead to ambiguous ordering."
    671     )

ValueError: All arrays must be of the same length

[zeecode07]

@brosaplanella how sir?

[brosaplanella]

I tried it with a short cycle (5 cycles) and works fine to me. 5000 cycles is a lot so you are trying to save a lot of data here. It is advisable to split the experiment and save smaller files anyway.