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A battery cell will generally carry an electric charge only for a limited amount of time, and most of the time it is difficult to tell how much of this charge remains. A useful item for determining the amount of power remaining in a battery is a battery tester, which can come in a variety of styles depending on what type of battery is being examined. Some battery testers are built right into the battery, others are built into the item that the battery is being used for, and most are portable and can be used for many varieties of batteries.
Some types of battery tester are designed to test multiple batteries. The most common of these multi-battery, or universal, testers are designed to check the available charge of household batteries. These can include AA, AAA, C, D, 9-volt batteries, watch-style (lithium) batteries and more. Analog testers use a needle on their display to show the battery’s power, while digital testers use a numeric LED display.
The tester usually contains slots for the battery, or two leads, which make contact with the positive and negative electrodes. An analog or digital display will then let the user know how much power is left in the battery that is being tested. Sometimes a battery tester is self-powered, meaning all of the energy that is needed to test the battery comes from the battery itself, while other types of testers require their own power source to operate. Others types of battery testers can be built right into the battery itself, and a common type of this battery tester uses a special type of conductive ink. When two leads are pressed, the ink will appear and shows how much power remains in the battery along a printed gauge.
Larger types of battery testers are designed for use on heavy-duty batteries like 12-volt batteries, car batteries and more. The displays on these testers can determine the remaining power of a battery in terms of percentage, which can be important in measuring the ability of the battery to start an engine. These automotive battery testers can also be designed to test other components of a car’s charging system, such as the alternator. Many also contain built-in chargers for immediate charging when a battery is low in power.