A mobile power supply is a device that provides power to portable electronic units through a wired connection or stored charge. External power supply devices are used to extend the usefulness of an electronic product beyond the limits of its internal battery. These units convert the electrical input from a wall or car lighter plug into a charge that is compatible with the paired device. Many varieties give the user the freedom to stay mobile by working as batteries to power electronic devices where no outlets are available. Most are designed for use with a specific device or type of device and have built-in features, like limiters and fuses, to prevent damage from excessive or insufficient power.
Phones, laptops, and other devices can all use mobile power supplies, and they are as different as the products they power. The sizes, styles, and outputs of the power units vary greatly and are changing rapidly as technological advances allow for more power to be stored in smaller and more portable packages. Most power supplies either plug directly into a wall outlet using an adapter cord or must be inserted into a unit-specific charger bases to be powered up. Either the charger base or the mobile power unit will often have a small LED indicator light. Color codes may vary by manufacturer, but most will glow red when they are drained and green once they are refilled and ready for use.
Each time a power supply is drained, it can be switched out with one that has been charging to provide continuous power without being tethered to a wall by a power cord. Purchasing multiple units for the same device allows the user to constantly have a charged one waiting. Some power tools have power supply packs that are compatible with the entire line of tools so that a charged one can be pulled right out of a tool that is not in use and attached to the tool the individual needs to use next. It is important for users to always read all the warnings and instructions on the mobile power supply to ensure compatibility and proper use before it is connected.
The charger or power cord for this device is often designed for the power outlet and electrical standards of one specific country or region. A special adapter may be necessary to charge a power supply that is designed for use outside the area a person is in. International power supplies usually come complete with multiple plugs for use in a variety of outlets.