The role of the battery!

Batteries and battery packs are an important part of using electronic circuits.  The battery allows the project to become independent of the programming computer.  Here is where a classroom problem can develop

Most development boards since 2000 relied upon battery packs that looked like these. The logic circuit on digitally controlled circuits will require 5 or 3.3 volts. It is important to separate the logic circuit from any circuits that might use "spikes" of electrical current.
A simpler solution, with similar cost, is to use a 9 volt battery pack and a voltage regulator.