The Newman, Tiedemann, Gu, and Kim (NTGK) and direct current internal resistance (DCIR) models are two simple semi-empirical electrochemical models that belong to the same group. The NTGK model was proposed by Kwon [[330]] and has been used by others [[314], [313]]. In the model formulation, the volumetric current transfer rate in Equation 19–4 is related to the potential field by the following algebraic equation:
 | (19–5) |
where 
denotes the active zone's volume of a single battery; 
is the battery cell voltage, which is either obtained directly from the
circuit network solution method or calculated as 
-
from the MSMD solution method; 
is the battery total electric capacity in Ampere hours; and 
is the capacity of the battery that is used in experiments to obtain the model
parameters 
and 
. 
and 
are functions of the battery depth of discharge (DoD):
 | (19–6) |
For a given battery, the voltage-current response curve can be obtained through
experimentation. Then 
and 
in Equation 19–5 can be fitted, in theory. There
are two approaches to specifying 
and 
functions:
- and can be fitted from testing data as functions of DOD and temperature
explicitly before simulations. The relationship between / and DOD/temperature can be provided:
through function forms as proposed in [330]
(19–7)
where
and 
are the battery-specific NTGK model constants.by a two-dimensional lookup table
- and are not determined in advance. Instead, the relationship of current and
voltage from raw test data is stored and and are computed on-the-fly during simulation.
Model parameters are battery specific. You can use the 
and 
parameters from a tested battery with capacity 
for a battery with different capacity 
as long as the battery's material is the same. If the model parameters are
from the battery that is analogous to the one you are simulating, then capacities
and 
will be the same.
In the formulation of the NTGK model, 
can be regarded as battery internal resistance. In applications where internal
resistance is known, it can be defined directly in Ansys Fluent. See Inputs for the NTGK/DCIR Model in the Fluent User's Guide for more
information.
The electrochemical reaction heat 
in Equation 19–3) is calculated as
 | (19–8) |
where the first term is heat due to overpotential and the second term is heat due to entropic heating.
For conditions where the electric load does not change much, the NTGK/DCIR model can be used for simulating the battery charging / discharging cycle. However, should the sudden surges in the electric load occur, such as in a real driving cycle, the NTGK/DCIR method will not account for the inertial changes. For simulations of such abrupt fluctuations in the electric load, you can use the Ansys Fluent Equivalent Circuit Model (ECM) model. See ECM Model for details about the ECM model.
For more information about setting up the NTGK/DCIR model, see Inputs for the NTGK/DCIR Model.