Many computing devices can either run off a battery or be plugged in, while others are made to run from the battery and be periodically recharged. Batteries are used in laptop computers, smartphones, mp3 players, and tablets. A battery meter, which may be part of the operating system or an add-on utility application, allows the user to quickly and easily learn the state of the battery in order to decide when recharging is needed, troubleshoot when some function is using too much battery power, or determine that the battery needs replacing with a new battery. To avoid confusion, it’s important to know that outside of computing, the term battery meter is used for devices that monitor the charge and voltage level for 12-volt vehicle batteries. The battery meter may appear on the screen or in the toolbar on Apple® devices or taskbar on Windows® devices, or both screen and bar. Depending on the device, a user may be able to choose whether to show only the icon, or the icon and either a percentage that tells what percent of full battery power is left or the estimated remaining time of use. While the percentage is absolute, the time remaining will vary, depending on the intensity with which the device is used. Watching movies, for example, will drain the battery more quickly than listening to music with the screen sleeping or using a word processing program. The battery meter is green on many devices while the battery is in the safety region. The battery meter will characteristically include a warning indicator when the battery is getting low to allow the user time to save work and plug in the device to start recharging. This warning is indicated by symbols or color changes, which vary with the device, but may be yellow or red, in contrast to the usual green color. Device makers offer advice on their websites for preference settings that can help maintain the longest possible battery life. Enabling screen dimming is a common suggestion, for example. Add-on battery meter programs, which are platform specific, may be freeware or paid. Sometimes the freeware is a lite version of a paid program, allowing the user to get a taste of the program’s value. A special battery meter application may provide more information that what the operating system offers, such as calculating the full lifetime of the battery, or identifying the charge rate.
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