Heat Transfer Coefficient Only Affects Temperature, Not Current/Voltage/Power

PyBaMM Q&A
1

Issue Description

I performed two discharge simulations with different heat transfer coefficient values (10 and 290) and noticed that only the temperature profile changes between the two cases. The current, voltage, resistance, and thermal power profiles remain identical.

Expected Behavior

I expected that changing the heat transfer coefficient would affect not only the temperature but also the electrochemical behavior (current, voltage, power) since temperature typically influences: Battery internal resistance, reaction kinetics, diffusion coefficients…

Observed Behavior

  • Heat transfer coefficient = 10: Temperature rises significantly during discharge
  • Heat transfer coefficient = 290: Temperature remains relatively stable
  • All other variables (current, voltage, resistance, thermal power): Identical profiles in both cases

Questions

  1. Is this the expected behavior in PyBaMM?
  2. Does the heat transfer coefficient only affect heat dissipation to the environment without coupling back to the electrochemical model?
  3. Are there specific model settings or parameters that need to be enabled to account for temperature-dependent electrochemical properties?

Simulation Details

  • Model: DFN model with lumped thermal model
  • Discharge conditions: Discharge at 4A for 3600 seconds
  • Heat transfer coefficient values tested: 10, 290

Attached Results

These are the graphs with 10 HTC

thermal_power_1C_variables_graph_10_HTCvalue
thermal_power_1C_variables_graph_10_HTCvalue1854×965 91.2 KB

and these are the graphs with 290 HTC

thermal_power_1C_variables_graph_289-16_HTCvalue
thermal_power_1C_variables_graph_289-16_HTCvalue1500×965 82.6 KB

Any insights on whether this is expected behavior or if there are additional settings needed to couple thermal and electrochemical effects would be greatly appreciated!

2

Hi Maguixx,

If this issue is still not resolved, I just wanted to add that it often occurs when fundamental variables with Arrhenius dependence have their activation energy values set to zero, set too low, or treated as constants. Please check parameters such as solid/electrolyte diffusivities and other parameters to ensure they include temperature dependence.

Thanks,

Sunil