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Author Topic: BayStack 5520-24T-PWR with -48V DC telecom power  (Read 2118 times)

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Offline marekm

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BayStack 5520-24T-PWR with -48V DC telecom power
« on: August 05, 2013, 08:29:12 AM »
Does anyone have any experience with powering these switches from -48V DC telecom power, which I have already available (feeding some other devices) and would like to feed the 5520 through the RPS connector (without the original RPS 15)?
I guess it's not officially supported as Avaya wants us all to buy the original RPS. but I've just purchased the switch second-hand with no official support, and perhaps someone did it anyway...  I know what I'm doing (I'm an electronics engineer now running a small local WISP, aware of electrical safety issues etc.) and I'm prepared to void the (long expired) warranty, just don't want to fry the hardware in the process.
My DC supply voltage can range from 45V to 55V depending on battery charge state, 55V most of the time (when AC power available and battery fully charged).  This is within spec for 802.3af powered devices, but is this safe for the switch itself?  Original RPS 15 spec says 47.5V DC but with no tolerance specified.
So far, I've just tried it (using a bench DC power supply, up to 55V with 2A current limit) and it seems to work fine as the only power source.  There is an issue if the DC voltage is above 48V and AC power is applied as well (redundant setup), this results in audible relay clicking very often inside the switch (it seems the built-in AC power supply doesn't like running with no load if the higher DC voltage supplies all of it).
Another question - I'd like to buy a matching 2-pin DC power plug (currently testing with crocodile clips), does anyone know what connector type / part number this is (what to ask Google for)?  (I mean connector only, not the ready made RPS cable, as I'd like to connect the other end to my own DC power supply, not the original RPS 15.)