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differences in the IR due to additional welds between tabs, etc., however, it is a good general
reference that higher cell count batteries (of the same capacity/C rating) will have higher IR than lower
cell count batteries.
A 3S 11.1V 2250mAh 45C battery will have approximately double the IR of a 3S 11.1V 4500mAh 45C
of the same make/model, condition, age, etc. This is because the 4500mAh battery has twice the
capacity and approximately ½ the IR as a result. Again, this is not an exact measurement, but is a
good general reference that higher capacity cells (of the same capacity/C rating) will typically have
lower IR than lower capacity cells.
A 3S 11.1V 2250mAh 45C battery will have lower IR than a lighter weight 3S 11.1V 2250mAh 25C
battery. General speaking, if properly rated, the 25C cells will have higher IR, hence the reason they
are only able to handle 25C versus 45C continuous discharge rates.
Some additional notes, hints and tips:
Regardless of the C rating, in most cases if the IR of one 2250mAh cell/battery is lower than that of
another 2250mAh cell/battery it will be capable of higher charge and discharge rates. However, in
some circumstances, due to the typical IR measurement method of most industry equipment, it is not
possible to account for all actual variables. For example, if a 2250mAh cell has slightly higher IR than
another 2250mAh cell when checked with the TP1430C, it is possible that under a higher load than
the TP1430C places on the cell, and with the associated heating in the actual application, the IR of
the cell actually changes to become lower than the other cell when used in the same application. This
can come as a result of differences in chemistry, materials, actual internal cell construction and/or
battery construction. As a result, while measuring the IR with a unit such as the TP1430C can provide
a good baseline reference, you should still take the time to test the batteries side by side in the same
application in case the other variables affect the actual performance accordingly.
Unfortunately it is not really possible to create a chart that shows what a good IR value versus a bad
IR value may be for a given capacity, C rating, make/model of cell/battery. Because even if a
cell/battery has twice the IR of another cell/battery of the same make/model, as long as it continues to
perform adequately in your actual application it is still very usable. In many cases if the IR of a given
cell/battery increases by 50+% from when it was new, it will typically offer noticeably less
performance. On the other hand, especially in lower discharge rate applications (such as slow flyer,
trainer and
‘cruiser’ airplanes), an increase in IR can have little to no noticeable impact in performance
for quite some time. Therefore, you should continue using batteries regardless of the IR if they
continue to perform well enough in your given application.
Also, the various equipment in the industry that offers IR measurement will measure and deliver
values based on their own methods and standards. As a result it is not practical to compare the IR
measurements for even the same make and model of battery on different makes and models of
equipment. And due to variations in the calibration of actual units, ambient conditions, etc., it is not
typically practical to compare the measurements for the same make and model of a battery on the
same make and model of equipment or even between the two ports of a dual port charger. Instead it
is best to make all measurements and to compare the relative results from a single port or the same
unit whenever possible.
To Measure Battery Internal Resistance
While on the Battery.IR screen/menu in the Data View Mode, simply connect the battery to the main
power/charge lead. Then, press the ENTER button once and after a relatively quick check the
charger will display the approximate IR of the battery. Again, this value is not absolute and will vary
per the variables previously noted, however, it is still a valuable reference. Also, if you continue to
