Testing Batteries  : purpose carbon-zinc batteries but last about seven or eight times as long. AI~.c batteries have a high capacity, are better at high and low temperatures, and r: long shelf life.
Nickel-cadmium batteries are sold as “ni-cds” batteries. Unlike the : batteries mentioned above, they are rechargeable batteries. When they run c: they can be put into a battery recharger and restored to life. Ni-cds cost abo..: times more than general-purpose carbon-zinc batteries and don’t last as 10-, alkaline batteries. However, they can be reused dozens of times.
The batteries above are the most common types for general use. Hov. ~ there are many other types as well. Mercuric-oxide (”mercury”) batteries are _ in electronic watches, calculators, and hearing aids. They are the “button” t\ =_ batteries about the size of a large, thick coat button.
Silver-oxide batteries are also button cells. They are also used in some: of watches.Lithium-manganese (”lithium”) batteries are used to power watches liquid crystal displays (the gray orgreen type of digital display). They have = button shape.Zinc-air batteries are used in pagers, hearing aids, and personal me: electronics. They are a fatter button battery.

A Little More About Batteries

Batteries store electrical energy. Generally, the larger the battery size more energy that can be stored. Batteries supply electrical current at a cevoltage. Current can be thought of as being similar to water flowing throi. ~ hose. Voltage can be thought of as the water pressure forcing current throug : hose. Some devices, such as flashlights and portable tape recorders, req; . great deal of current and run down batteries quickly. Other devices, sueremote controls for televisions and video cassette recorders, require ver, current and do not run down batteries very quickly at all.
In addition to material used and physical size, batteries are rated in vo .: and the amount of energy they store. The voltage of a battery is the amou “force” required to push the current through a device. Common voltages arC’ volts (flashlight cells), 6 volts (lantern batteries), 9 volts (transistor radios anc . equipment), and 12 volts (camcorders). A higher voltage battery isn’t betterjust designed to work with a certain device at that voltage. Replace batteries. ones of the same voltage.
The amount of energy stored is often not given for common batteries, sue A, AA, B, C, and D cells. Batteries for high-current requirements, such as carr : ders, are sometimes rated in mAh - milliampere-hours. The higherthis rating longer the battery wi II last. A mAh rating of 2000 mAh means that the batter. last twice as long as one with a rating of 1000 2mAh.