Nottingham,
UK on
October 25th.
Go to www.
roamingrob
ots.co.uk for more details.
Franklin Institute Robot Weekend
will be held on October 11th
in Philadelphia, PA. Go to
www.nerc.us for more details.
Mecha-Mayhem 2008 will be
held on October 16th in
Rosemont, IL. Go to
www.the
crca.org for more details.
2008 Halloween Robot Terror
will be held on October 25th in
Gilroy, CA. Go to
www.calbugs.
com for more details.
Robots Live will hold events at
Reading on October 11th,
London on October 25th,
Chester on November 15, and
Birmingham on November 22nd.
Go to
www.robotslive.co.uk for
more details.
Antweight
Benelux
Championship
will be held
by Dutch
Robot Games
in the Netherlands on November
1st. SV
BUILDING BATTERY
PACKS FIT FOR C MBAT!
● by Robert Wilburn and Paul Reese (Team O-Town Robotics; teamotown.com)
In the early days of combat robotics, builders were often forced to
assemble their own battery packs if
they wanted something robust that
would tolerate conditions filled with
shock, vibration, heavy G-loads, and
constant flexing all while operating
at very high temperatures. This is no
longer the case with numerous
venders offering proven off-the-shelf
solutions. As vender packs became
the norm, we continued to build our
own packs using techniques we had
learned through trial and error.
These techniques can be applied to
pack assembly for many uses
outside of combat robotics. This
guide will cover some of the
advantages and disadvantages of
existing battery chemistries, as well
as describe the step-by-step process
we used for pack construction.
Following these simple techniques
will ensure you make battery packs
that are fit for combat!
Before we get started, let’s talk
about SAFETY. First, realize that a
battery is a form of stored energy.
Typically, this energy is used in small
quantities over long periods of time.
However, if this energy is consumed
in a very short period of time — say
from a short circuit — conditions
may occur that pose a serious
safety hazard.
A shorted battery may produce
enough heat to cause severe burns,
may explode, or possibly combust.
Before attempting any steps in this
process, take the time to familiarize
yourself with your tools, work surface,
environment, and the fundamentals
of battery operation. Extreme care
should be taken to never short the
cells. This is a fairly simple process
and one that just about anyone
with the required materials can
accomplish (see Parts List).
Nickel-metal Hydride
(NiMH) and
Nickel-cadmium
(NiCd) Chemistries
The debate over which of these
chemistries is better has endured
more than a decade, but suffice it
to say each has its advantages and
disadvantages. The choice should be
based on your application and your
research. Factors such as maximum
discharge current, series resistance,
cycle life, and self discharge are
specifications to consider. Generally
speaking, NiMH are the better choice
these days. The high current drain
advantage NiCds once had has been
diminished with advances in NiMH
design. Both chemistries have a
nominal 1.2V/cell under load. Either
chemistry could be used in the
following guide. The key here is to
do your research before choosing!
Lithium-ion and
Lithium Polymer
Chemistries
Lithium-ion and lithium polymer
are much newer and superior
battery technologies in terms of
Parts List
• Individual cells
• Bus bars
• Solder and soldering iron with
large tip
• Shrink tube — high temp variety
• A tube of Shoe Goo™
• Stranded copper wire — black
and red
• Dremel type tool with a small
carbide grinding tip
• Shrink wrap
• Heat gun
SERVO 10.2008 27
