High Rate Discharge Batteries
These are used in UPS systems primarily where there is a response required within a certain timeframe. X amount of power needs to be provided for 15 mins before the battery voltage drops too low and the system needs to shut down. This is why the batteries are rated for X watts for 15 mins. If grid/mains power goes down in a building a UPS system that is either part of the system/building wiring or installed at each desk instantly takes over the demand of power for all the equipment currently being used like computers, phones, routers, wireless access points. A UPS can be connected via USB cable to the computer and it sends a command to the computer to shut down if it's about to run out of power, therefore, saving any work you were doing and not corrupting the harddrive. In a large installation, a secondary system like a generator will supply power within 5 minutes or so until mains power is restored.