Specifications

useful built-in function for
quick setup and testing.
Battery discharge can also be
tested with the provided
program under the “Software
Examples” section of this note.
Additionally, small changes to
the program will offer even
greater control for the test,
allowing measurements to be
made under different modes
and settings. The following
describes the discharge test
setup for a consumer “AA” size
battery. Similar setups can
also be used for other types of
batteries.
Setup
Connect the battery to the DC
load. You can either solder
wires to the battery or use a
battery holder.
DC Load Setup
The setup is controlled by the
program, but be sure to
manually set the voltage and
current range prior to running
the test program. If the
current is reasonably large,
you might also want to
suggest they use the remote
voltage sensing feature of the
DC load.
Results
Provided as an example is a
plot (see Figure 6) of the
battery discharge curve for the
AA Alkaline battery tested with
the setup in Figure 5. The
command line used to run the
program for the data is shown
in Figure 7. The settings of
the command are indicated in
order as set to com port 5 in
constant current mode with
0.5 A and a cut off voltage of
0.5 V. The file name for the
data file is aa_test and “78deg
F” is a string included at the
end of each line of the file.
Note: For more details on the
program commands and to
run the test, find the
instructions and use the
python script provided
towards the end of this
application note categorized
under “Battery Discharge
Test”.
Battery Internal
Resistances
The DC load is an effective
tool for measuring the internal
resistance of a battery. The
battery is typically modeled as
the dashed area in the circuit
illustrated in Figure 8. The
voltage source V
o
is considered
ideal and is the open circuit
voltage of the battery. The
internal resistance R
i
is used
to idealize the internal losses
in the battery when current is
flowing. If the battery's
electrochemistry is regarded
as a network of voltage
sources and resistances, then
V
o
and R
i
comprise the
Thevenin equivalent circuit.
For alkaline batteries, the
internal resistance goes up as
8 of 17
Figure 6. AA Alkaline Battery Discharge Curve
Figure 5. Battery Discharge Test
Setup
+
AA size battery -
DC Load
+ -