What is the difference of the Circuit Network and MSMD option of the Battery Model?
The Circuit Network option solves only one potential field, and only if Joule Heat in Passive Zones is enabled. The MSMD solves 2 potential fields.
You could think of the Circuit Network option (when using the ECM submodel) as if the Voc, Rs, R1, C1, R2, C2 for each battery cell are arranged in Twin Builder and solved. There is exactly one set of ECM parameters for each cell. And you get one heat source for each battery cell.
Note that the voltage distribution in the busbars is ignored, the connecting wires are ideal wires with zero resistance. The single potential solved in the busbars and tabs is not feed back to the Circuit Network calculation.
When using the MSMD option with clustering of 1x1x1 it does similar things as the Circuit Network option. But in this case the voltage losses in the busbars and tabs are taken into account. As the 2 potentials are coupled by source terms for the transfer current only, convergence of the MSMD is less rapid as compared to Circuit Network option.