Shallow-depth rackmount external battery pack offers extended battery runtime when used in conjunction with compatible UPS systems. It supports configuration in rackmount applications using only 4 rack spaces (4U). It includes heavy gauge cabling with high current DC connector for simple installation. Additional output connector allows multiple battery packs to be daisy-chained to the UPS for even longer extended run operation. It includes hardware for 2-post rackmount installation and supports optional 4-post rackmount installation with addition of 4POSTRAILKIT accessory kit. It is ideal for installation in wiring closet applications.