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108 Making Things Move

All batteries are not created equal. To help you find the best battery for your
application, read on. We’ll look at different kinds, including rechargeable batteries,
and highlight the pros and cons of each. 2

Zinc
Zinc batteries are super cheap, and come in all the common sizes (D, C, A, AA, and
AAA). They can be rejuvenated a few times before their life is over with a special
charger. However, their internal resistance is high, and they don’t last very long.

Alkaline
Standard alkaline batteries (think Duracell CopperTop) last three to eight times longer
than zinc batteries. They also cost twice as much, and standard ones can’t be
recharged. There are rechargeable alkalines, but you need a special low-current
recharger that can’t be used on other rechargeable batteries. They also make
high-tech alkaline batteries that last two or three times longer that standard alkalines,
but they’re significantly more expensive.

Alkaline technology was not designed to handle the high levels of current that some
motors require, so these batteries may not provide power fast enough. They also
provide a decreasing voltage as they drain, which can cause problems if you’re already
on the edge of the voltage range of a motor or other component in your project.

Nickel-Metal Hydride
Nickel-metal hydride (NiMH) batteries are the best rechargeable batteries for the
projects in this book and the most common kind of rechargeable battery you’ll find in
stores. They have low internal resistance and can be recharged over 400 times in their
life. They don’t last quite as long as alkaline batteries, but they are improving. NiMH
batteries charge quickly (in an hour or two).

The main disadvantage is that NiMH batteries don’t hold a charge well. A fully
charged battery will discharge all by itself just by sitting on a shelf for a few weeks or
even days. For this reason, check battery voltage with your multimeter before use to
avoid frustration.

Unlike zinc and alkaline batteries, which provide the standard 1.5V, NiMH batteries
provide only about 1.2V. As a result, they are not always a valid replacement for
nonrechargeable batteries (though most consumer products that take batteries will
work with either).