The Ansys Fluent battery model can handle both external and internal short-circuits.
External Short-Circuit
In the case of an external short-circuit, battery's positive and negative tabs are connected
directly with no electric load. In Ansys Fluent, an electric load boundary condition for the external
resistance enables you to directly specify the total external electric resistance,
. The battery model solver will guarantee that the ratio of the battery's tab
voltage, 
, to the tab current, 
, equals the specified resistance value:
Internal Short-Circuit
Under normal battery operation, the battery’s positive and negative electrodes are divided by a separator, usually a thin polymer material that prevents electrons from traveling directly from the negative electrode to the positive electrode. In the case of an internal short-circuit, which could be a result of a nail penetration or a crash accident, the separator is ruptured in a localized area. Besides providing the normal tab current, the battery produces a secondary electric current from electrochemical reactions that is wasted through the shorted area.
The short-circuit intensity can be described by a fundamental variable-volumetric contact
resistance, which could be computed as 
, where 
is the contact resistance of the electrode sheet in the unit of
Ω·m2, and 
is the specific area of the electrode sheet in the battery volume in the unit
of 1/m. In the MSMD solution method, the sandwich-style electrode layers are not resolved;
instead, they are treated as a homogeneous medium. So, the combined variable—volumetric
contact resistance 
in the unit of Ω·m3—is used in the
calculation. The transfer short current density, 
in Equation 19–4, and extra heat generated due
to the short are computed as:
 | (19–32) |
The above formulation is general enough to cover non-short cases where 
tends to infinity. Contact resistance could be a function of time and location,
therefore allowing the dynamic evolution of the changes in the size of the shorted region and the
intensity of the short-circuit current.
For information on how to use and set up this feature, see Specifying External and Internal Short-Circuit Resistances.