CHAPTER 7 ■ NINE-VOLT BATTERIES
Alternatively, another robot was a little too slow and a little too weak in a robot Sumo contest. The
motors were nominally rated for 12 volts, so it was safe to upgrade to a fresh 11.2 NiMH battery.
By using a standard-size battery in your robot, regardless of whether it is 9 V, AA, AAA, C, D, or whatever,
you can switch between battery chemistries to adjust performance. That’s a good trick to remember. It is a
lot easier and faster to switch batteries than to rebuild your robot or alter the software five minutes before a
competition.
Mounting Batteries
Batteries tend to be one of the heavier parts in a robot. For this reason, the battery in Sandwich is mounted
near the wheel axle (see Figure 7-17). That way, most of the battery weight is on the tires (adding traction)
rather than on the front part (which drags).
Figure 7-18. Spot the copper tops! There are two batteries hiding inside this robot. Your job: find them
Figure 7-17. Battery mounted near rear axle
Since a robot’s battery is going to be replaced often, you want to make sure it is placed in a location that
is easily accessible. I made a mistake in my mini-Sumo robot, Bugdozer. The batteries are stored underneath
the wires and circuitry (see Figure 7-18), requiring most of the robot to be disassembled to swap in a fresh
power source.