Some notebook computers are designed with a dedicated battery for backing up RAM ( Random Access Memory) functions when the machine temporarily loses power from the main battery, when the lid is close or with a combination of "hot" keys. This feature allows users to change the main battery pack without losing the current applications and settings residing in memory. This is called a "battery hot swap" - switching the main battery pack without having to turn off the computer.

Most RAM batteries are rechargeable NiCad or NiMH and will last around 2-3 years. It is recommended that you replace your notebook's RAM battery when replacing the CMOS battery.

Also known as bridge batteries, RAM batteries, auxiliary batteries or resume batteries.