Page 210 - Robot Builder's Bonanza

Chapter 18

All about Batteries

orget miniature atomic piles. Forget dilithium crystals. The robots in science fiction are
Fseldom like the robots in real life. With few exceptions, today’s robots run on batteries— the
same batteries that power a flashlight, portable CD player, or cell phone. To robots, batteries
are the elixir of life, and without them, robots cease to function.
To be sure, batteries may not represent the most exciting technology you’ll incorporate
into your robot. But selecting the right battery for your bot will go a long way toward enhanc-
ing the other parts that are more interesting. Here’s what you need to know.

An Overview of Power Sources

Before getting waist- deep in the big muddy of battery selection, let’s first review the practical
power sources available for use with mobile robots. Note the word practical, m’kay? There
are plenty of potential power sources available in the world. Some forms of power are not
suitable because of their size, safety, or cost.

• Windup mechanisms provide power using tension that is slowly released. A common type
is based on the idea of a clock mainspring. These use a metal coil as a tension spring. The
coil powers a shaft or other movement as its tension is relieved. For robotics, the typical
windup mechanism is confined to small toys, particularly older collectable toys.
• Solar cells get their power from the sun and other light sources. A disadvantage of solar
cells is that power is directly related to the intensity of the light. Robots that use solar power
are often equipped with a rechargeable battery or a large capacitor; both store the energy
collected by the solar cell for later use.
• Fuel cells are gaining in popularity as an alternative energy source. Most use hydrogen in
a complex chemical reaction that produces heat, as well as a flow of electricity between
two electrodes.
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