by Alonzo Trueland
Battery Analyzer for
To “Charge It” or Not to “Charge It” is the Question
Knowing the discharge characteristics of the
battery in your portable drill may not be very
important, but having this kind of information is
vital if you want to be competitive in any type of electric
RC event. I was rudely reminded of the need for such a
device when my electric boat stopped in the middle of the
lake! It was only two minutes into its run that should have
lasted six minutes when it gave-up. I suspected the
battery was bad, but this should not be the way to find
out! If I was able to monitor the batteries performance
during its usable life span, a problem may have been
detected. If you know what your battery is capable of, it is
easier to develop a winning strategy.
This battery analyzer project is designed to test the
“health” of battery packs used in radio-controlled vehicles
to drive their motors. An effective way to test the health
of a battery pack is to place a normal operating load
on a fully charged pack, and then record the voltage
The project is relatively simple to assemble, but the combination
of software and hardware could be difficult for a novice to
troubleshoot. The high-current nature of this project requires sound
assembly techniques. Bad connections, excessive wire, insufficient
heat dissipation, and poor assembly are some things that
could cause frustration or possibly injury. An intermediate level of
experience with the outlined software and their associated tools
will be needed if the builder wishes to modify the programs.
levels while it is discharging through a test load. The
information produced from the recorded data will create
a graphical “discharge curve” that can be used to
examine its performance level and determine the health
of the battery under test.
The battery analyzer covered here can be divided into
three main parts: the test-load, interface board, and
computer program. The test-load provides a controlled
discharge current for the battery under test. The interface
board measures the battery voltage during testing and
transmits the data to the computer. The computer program will display the test information in a graphical form
and provide the means to save the data for later review.
Figure 1 shows the analyzer on the bench and ready to
dish-out some battery pack punishment!
Figure 2 shows how the battery connects to the test-load using the standard connector that comes with most
pre-assembled battery packs. The load is a simple voltage divider made with two 0.3 ohm 50 watt power resistors mounted to a large heatsink. The total 0.6 ohm load
will provide a 12 amp test current for a 7.2 volt six-cell RC
battery pack. The voltage is measured at the center of the
divider giving the tester a theoretical maximum battery
input voltage of 10 volts. At 10 volts, the divider will limit
the input to the data collector board to five volts. The
practical test voltage should be limited to 7.2-8.4 volts
Figure 1. Analyzer on the bench.
Figure 2. Battery connected to the test load.
NUTS & VOLTS