Featured This Month:
Features
22 BUILD REPORT:
Building a Better Battery
System
by Zac O’ Donnell
24 MANUFACTURING:
Creative Armor:
Sandwiching with Shock
Mounts
by Blake Hooper
31 PARTS IS PARTS:
Screwdrivers: Straight Up
by Nick Martin
Events
26 EVENT REPORT:
Halloween Robot Terror
by Dave Wiley
28 EVENT REPORT:
Roaming Robots UK
by John Frizell
33 November 10 – December 8
Results
ROBOT PROFILE – Top
Ranked Robot This Month:
30 Tourinho by Kevin Berry
22 SERVO 02.2009
BUILD REP RT
Building a Better Battery System
● by Zac O'Donnell
My 12 pound combat robot
Scurrie was designed to
use two battery packs that were
physically and electrically separate
from each other. The pack used
exclusively for the weapon
consisted of twelve 1,700 mAh
cells in series, while the drive
pack consisted of six of the same
cells. I had purchased the cells
long before for a different project,
so they fit my budget nicely.
However, they weren't the best fit
for the robot. The combined
weight of the two battery packs
was a pound and a half, and I
wanted to bring that down to
less than a pound so that I could
use the extra weight to improve
the reliability of the drive system.
So, how was I going to cut
my battery weight by 30 percent
while maintaining the same
power for the weapon and drive
system in a three minute match?
The answer was to find a newer
technology. The 1,700 cells were
nickel-metal hydride which was
the most advanced technology
when I bought them. However,
four years turns out to be a long
time in the battery industry. Two
new options had become
available that offered higher
energy density: lithium
polymer (LiPo) and batteries
from A123 Systems. I
needed a battery that was
rugged, could handle high
charge and discharge rates,
was not too expensive, and
— most importantly — would
meet my power and space
requirements in less than
a pound of total weight. A
PHOTO 1. Scurrie after taking first place at the
Franklin Institute 2008 competition.
