Batteries are all over the place -- in our cars, our PCs, laptops, portable MP3 players and cell phones. A battery is essentially a can full of chemicals that produce electrons. Chemical reactions that produce electrons are called electrochemical reactions. In this article, you'll learn all about batteries -- from the basic concept at work to the actual chemistry going on inside a battery to what the future holds for batteries and possible power sources that could replace them!

Many lithium ion packs have a built-in meter consisting of a row of LEDs and a button. To accurately report the state of charge, the pack electronics has to keep a record of the current in and out of the cell, as well as a model of its behaviour. This can become more inaccurate over time; more modern cells will recalibrate themselves.

However, batteries are not quite that linear. For one thing, all batteries have a maximum current they can produce -- a 500 milliamp-hour battery cannot produce 30,000 milliamps for 1 second, because there is no way for the battery's chemical reactions to happen that quickly. And at higher current levels, batteries can produce a lot of heat, which wastes some of their power. Also, many battery chemistries have longer or shorter than expected lives at very low current levels. But milliamp-hour ratings are somewhat linear over a normal range of use. Using the amp-hour rating, you can roughly estimate how long the battery will last under a given load.

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