1C charging rate fills battery in 20 min

[skywo1f]

I am running a sensible LFP model based on Prada2013. By sensible, I mean I changed the min and max voltages to
` "Lower voltage cut-off [V]": 2.5,

   "Upper voltage cut-off [V]": 3.65,

my code is:import pybamm

#chemistry = pybamm.parameter_sets.Prada2013
param = pybamm.ParameterValues("Prada2013")

exp = pybamm.Experiment(
[
(
"Charge at 1 C until 3.65 V",
"Hold at 3.65 V until C/10",
"Rest for 5 minutes",
"Discharge at 1 C until 2.5 V",
"Rest for 5 minutes",
)
]
)

#model = pybamm.lithium_ion.DFN()
model = pybamm.lithium_ion.SPM()

sim = pybamm.Simulation(model,experiment=exp,parameter_values=param)
sim.solve([0, 3600],initial_soc=0) # solve for 1 hour
print(sim.parameter_values)

sim.plot(

[
    "Current [A]",
    "Terminal voltage [V]"
]
)

`

So I start at 0% SoC, charge at 1C, but then the battery is charged in 20 min (see image). Any idea what I am missing?

[skywo1f]

the issue seems to have something to do with changing
"Nominal cell capacity [A.h]": 5.0,
(I changed it from 1.1 to 5). It's like it didn't change the actual capacity of the cell, just changed what amperage C corresponds to.

[skywo1f]

(current function and typical current don't seem to change much)

[skywo1f]

if I change
"Number of electrodes connected in parallel to make a cell": 4.0,
(from 1 to 4) then it charges at 1C for an hour. But I am not sure how that makes sense.

[rtimms]

Nominal cell capacity [A.h] is used to convert between current and C-rate. Since you changed the voltage limits, you changed the useable capacity, so you’ll need to figure out what the new capacity is.

Current function [A] sets the current when you aren’t using an experiment. Typical current [A] is just used internally for scaling and shouldn’t affect the results.

[skywo1f]

setting the Ah seems a bit artificial. Is there any way to give Pybamm the battery parameters and have it calculate Ah?

[rtimms]

Give the electrode capacities, total cyclable lithium, and voltage limits you can calculate the cell capacity as in this example.

The parameter Nominal cell capacity [A.h] is simply used to convert between current and C-rate.

[1836005678]

If we change upper and lower voltage limits, then the nominal capacity may also changed.
However, discharge Prada2013 battery at 1C(5A) from default setting(3.6V) to lower voltage cut-off(2.0V) last only 0.75 hour, much shorter than 1 hour. The Prada2013 parameter set may have some problem.

[rtimms]

Yeah, I think the Prada set needs some updating (e.g. see #1811). If you take a look at the docstring in this file you’ll see it’s a combination of data from a number of papers, then fitted to data from the Severson Nature paper from 2019.

If you make any progress it would be great if you could open a PR to update the parameters.

[rtimms]

This thesis might be a helpful starting point.

[1836005678]

After applying your suggestion, simulation result seems correct. Detailed results have been descripted in my comment in #2661.
5 parameters have been updated in PR https://github.com/pybamm-team/PyBaMM/commit/ac93b8c5cd87683c9f251a787fee886afe4e74b7.
Thank you very much!