Would you install a rackmount or external battery extension pack?

A rackmount UPS may include a built-in battery or require an external battery pack which can be housed in a rack mountable tray or a metal cabinet. If there is space within the server rack then it can make sense to install the battery tray internally underneath the UPS system. If there is little or no internal space then the battery pack will need to be placed external to the server rack and supplied as a floor standing battery cabinet. This applies to small power ratings and short duration runtimes.