A battery backup, or uninterruptible power supply (UPS), is primarily used to provide an emergency power source to key hardware components of desktop computers.

In most cases, this hardware consists of the main computer housing and the monitor. However, depending on the size of the UPS, other devices can also be connected to a UPS as a backup power source.

In addition to acting as a backup when the power goes out, most battery backup devices also act as power "conditioners" by ensuring that the electricity flowing to your computer and accessories is free of dips or spikes. If a computer does not receive a consistent flow of electricity, damage can and often will occur.

Although a UPS system is not required for a complete computer system, it is always recommended to include one. The need for a reliable power supply is often overlooked and not fully realized until damage has occurred.