Page 222 - Robot Builder's Bonanza

USING A PREMADE BATTERY PACK 191

+ volts

Voltage
Battery
supply
symbol
symbols
Figure 19- 1 Various common battery
0 volts symbols used in electronic diagrams. This
or ground book uses the ones on the left and right.

There are lots of different names for the ground connection. You may also encounter common,
G negative, 0 volts, 0V, return, chassis, and earth. These terms don’t always mean the same thing,
depending on the application. But for general electronics and robotics work, unless otherwise
noted in the description of the circuit you can assume the terms are interchangeable.

Using a Premade Battery Pack

Many of today’s consumer products use rechargeable battery packs. So can your robot. The
battery pack can use cells that fit into all shapes and sizes of battery compartments. Wires and
a quick- disconnect plug allow easy removal of the batteries, for things like recharging or
replacement.
You can rob the battery pack out of a discarded consumer electronics device, such as a
cordless phone you no longer need. You’ll then have batteries for your robot, as well as the
charger that came with the phone.
Or you can purchase replacement packs, though these can carry a premium price. This
approach is worthwhile only if you already have a recharger for the pack. Otherwise, you’re
better off using battery packs designed for radio control (R/C) applications, as detailed next.

USING PREMADE R/C BATTERY PACKS

Radio control (R/C) applications, like model airplanes and
From 4.8v
battery model cars, are power hungry. High- capacity rechargeable bat-
pack tery packs are the norm. The packs are available in a variety of
voltages and capacities from any local or online store special-
izing in R/C cars and planes. Common packs voltages are:

4.8 volt
7.2 volt
9.6 volt

The 7.2- volt packs are perhaps the most useful for robotics. Note the fractional voltages in
this list. These are the result of the 1.2- volts- per- cell batteries used inside the packs. Current
capacities range from about 350 milliamp- hours (mAh) to over 1500 mAh. The higher the
current capacity, the longer the battery can provide juice to your robot. Unfortunately,
higher- capacity batteries also tend to be larger and heavier.

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