Reserve Batteries
Stand-by batteries or Reserve batteries are used in applications where there is mains power supply available but a battery is used as a power source if the mains power goes out. The first and most common example is a buildings/home alarm system is where a battery is part of the system design but not commonly required to provide power unless there's a power cut. UPS (Uninterruptable Power Supply) they sit under your desk in the office and your computer plugs into it if there's a power cut the battery provides power to keep the computer on so it doesn't corrupt or lose your data for a short period of time. it's a just-in-case source of power.
These batteries typically come in industry-standard sizes available from almost all battery distributors and have a 3-5 year design life or long-life design is 10 years. Service life and warranties are often 1 year for a 3-5 year battery and 3-5 years for a 10-year battery.
Again with many types of battery they can have dual purposes, so a deep cycle industrial design battery can be used for stand-by applications but not high rate discharge, and a general-purpose standby battery can cycle but not deeply or for many times.
