POE Battery Survey Toolkit
PoE (Power Over Ethernet) isn't as simple as just providing 48V.  There is some analog signalling that goes back and forth.  A PoE power supply isn't allowed to provide the 48V until some negotion has occurred.  On the device end, it might just work if 48V is always applied, assuming the device was designed to handle that (is PoE capable).  However, that is outside the PoE standard so it is not guaranteed.