Discharge current proportional to cathode thickness

[marbris]

Hi,

Great Program! The program seems to have an unintuitive way to set the discharge current and I'm not sure if it's a bug or if I'm doing it wrong. It seems to me that if I set 1C_current_density = 1 and Crate = 1, the simulation should represent a discharge of 1 A/m2. However, by way of scaling, the program actually calculates the current with

currset = 1C_current_density * Crate * L_c / (e * ( 1 - poros_c) * P_L * rho_s * Damb)

In my simulations I'm looking to discharge cathodes with different thickness (L_c) at the same discharge current density. But If I double L_c, so will the discharge current. So I have to scale 1C_current_density with 1/L_c to make sure the current doesn't change across cathodes. This doesn't seem to be the intention behind 1C_current_density.

Furthermore, if you leave 1C_current_density empty, the current is instead calculated with

currset = Crate * L_c**2 / (3600 * Damb)

This, too, doesn't seem right. At a constant C-rate, the discharge current should be proportional to L_c, not L_c**2. The workaround (scaling with 1/L_c) is simple enough, but is this right?

I'm using version 0.1.8. If it helps, I'm deriving this from
mod_cell.py line 378
configuration.py lines 436-444, 480
derived_values.py lines 173-177, 157-160, 146-149, 141-144, 184-187, 189-198

Thanks
Martin

[d-cogswell]

Hi @marbris, it sounds like you need to define a current density rather than a C-rate. You are correct that there isn't a way to specify a current density at the moment, but we are almost done with a pull request #84 which allows either C-rates or current densities (as well as more complicated battery cycling protocols). Would you like to give it a try? Alternatively, we could help you modify your existing code.