post-apocalyptic Atlanta. NiCad
batteries are easily found as the
power source for power tools. All it
took was a trip to Harbor Freight to
pick up a couple of drills with
NiCad battery packs to help give
Troublemaker its upgrade.
The drills we found happened to
have 24V battery packs — higher
voltage than most power tools
(which usually clock in at 12V or
18V). The batteries were also rated at
1.3 Ahr, which was a decent capacity
the bot throughout the matches.
Another advantage of the NiCad
packs is that they did not require
much modification to be
implemented in the bot. Removing
the top of the plastic covering was
enough to expose the contacts to
the cells, and we wired a milspec
connector directly to them (since that
was the type of connector that came
with Troublemaker’s original lead-acid batteries).
We wanted to keep the milspec
connectors because they locked in
place when connected, were tightly
sealed, and if they were meant to
survive the rough and tumble world
of Champ car racing, we figured
they could handle combat robotics.
To seal up the battery contacts
and to provide some stress relief, we
coated the contacts in silicone gel.
The batteries were a perfect size to
mount in the center of the bot, and
the bolt holes in the existing plastic
casing provided an easy way to
mount the batteries in the bot.
The NiCad batteries also allowed
us to make a more fundamental
change to the circuitry of the robot.
The previous racecar batteries were
12V. Though the bot had two of
them, they were wired in parallel so
the overall voltage of the bot was
The new batteries were 24V
batteries (we also wired two packs
in parallel), which was just peachy
with most of the components of the
bot (the Victor speed controllers
were fine with 24V, and the Maxon
drive motors are rated for 5V-30V).
Our kinetic weapon, however,
was powered by a cooling fan motor
from a car that was ostensibly rated
Overvoltaging the motors can
result in a few things: It increases
the power of the motor, which can
mean an increase in RPM and
torque. It can also burn out the
motor. We knew the 24V packs
were a risk, but the motor performed
well throughout Botbash 2003, we’re
sticking to our overvoltaged guns.
72 SERVO 02.2014
OPENING UP THE LI-POLY PACK.