A system and method for supplying uninterruptible power includes a housing, a power supply input for a DC power source, a power source equipment input, a powered device output, an alternative power supply, a control module, and a power source equipment extension. The control module includes a comparator, a switch, a line filter and protector and an injector. The injector includes a regulator and PoE power management module. The alternative power supply includes a plurality of battery packs in series. The system can be located at a remote location with only DC power sources, such as generators, batteries, and solar cells.