You have a friend over for a sleepover. You've built your fort out of pillows and blankets. Now, it's time to raid the refrigerator. It's really dark, though, so you need a flashlight to navigate the dangerous path to the kitchen.

Luckily, you thought ahead and stashed a flashlight in your pillowcase. With flashlight in hand, you creep out of the fort and slide the switch to the “on" position. But nothing happens. You're still stuck in the dark.

You've just been struck by that age-old problem: dead batteries. Without those little packets of stored energy, your flashlight is nothing more than a paperweight. You'll have to make it to the kitchen in the dark, since that's where the spare batteries are stored!

Depending upon the type of flashlight you have, it could take any one of several types of batteries. Does it use big “D" cell batteries? Or perhaps it runs on smaller “AA" or “AAA" batteries? And what's the big deal with all these letters on batteries anyway?

A trip to the battery section of your local store will reveal a large selection of batteries of different sizes. Some of the most common types of batteries you'll find there are “AA," “AAA," “C," and “D" batteries. A look around your house will reveal many other types of batteries, too.

There's the automobile battery in your car. Your lawnmower may have a battery. All sorts of electronics, from watches to MP3 players, have batteries, too. Some of these are tiny lithium-ion batteries that are smaller than most buttons! All in all, there are hundreds of different types of batteries.

Why do batteries come in so many sizes? And how did they get their names? Let's take a quick look at the history of these little packages of stored energy.

As far back as 1749, Benjamin Franklin used the term “battery" to describe the set of linked capacitors he used to conduct (pun totally intended!) his experiments with electricity. It wasn't until the late 1800s and early 1900s, though, that batteries became popular as a power source.

As a source of power, batteries convert stored chemical energy into electrical energy. They have been used to power all sorts of devices, from automobiles and watches to appliances and lights.

Given the wide range of uses for batteries, it's no surprise that many different sizes and types needed to be developed. Larger objects need more power, so larger, more powerful batteries had to be developed. As technology led to smaller and smaller versions of things, smaller, less powerful batteries were needed.

However, battery manufacturers soon realized that some common standards would be needed in order to avoid the need for developing a new battery for every new idea that came along. In 1924, a group of people from the battery industry, along with several manufacturers and government agencies, met to propose a standard system of battery sizes.

They decided to use the letters of the alphabet to designate a standard set of sizes. Thus, from the start, there were “A," “B," “C," “D," “E," etc. batteries. This worked fine for a while, but eventually a need for even smaller batteries arose. After World War II, “AA" and “AAA" batteries were developed for smaller applications.

Over time, some of the types of batteries simply died out, because they were no longer used in any products. For example, you won't find any “B" batteries in most stores today. Some manufacturers may still make them for a very limited range of products. They did exist and were popular at one time, though!

Wonder What's Next?

Tomorrow's Wonder of the Day is really, really shocking!