PS for a Cisco AP

[Aalelan]

Ok, here is my situation. I have an old Cisco Wireless Access point that runs on 48vdc but is missing the power supply. I want to use it and have the current situation.

I have an external battery array for my 2200VA UPS that is 48VDC 74AH convenient huh? Well here is the problem, at a full charge and setting on the trickle from the UPS the voltage is right around 53vdc, and when the UPS has been on battery for a while the voltage gets down to 45vdc (granted that is a long while)

I want to be able to tap off of this battery bank to run my AP but I want to insure i get some clean constant +48vdc input for it. I'm looking for a simple circuit design to do this..

One friend here at work provided me diagrams for boosting voltage if I wanted to use one segment of the pack but not how to ensure the voltage is regulated. I would prefer to use the whole bank of batteries as my voltage source as to keep them “balanced” during discharge.

Any help or suggestions is appreciated, I know this is a little out of the normal for this forum or at least this section but I was not sure where to put it at..

[999999999]

Re: PS for a Cisco AP

Open the AP and see what the power input stage looks like. It's doubtful anything (but "maybe" an industrial fan which isn't picky about voltage this much) uses 48V, that the voltage is so high to allow low current for PoE purposes if/when desired.

I'm suggesting that right after that 48V input, most likely everything is fed from a buck (switching) regulator stage (or two, then linear) that is quite tolerant of a minor voltage variation between 45V-53V when the nominal is spec'd as 48V. With that 48V spec, even the caps aren't likely to be merely 2V higher as 50V spec, would typically be at least 63V if not higher spec like 80 or 100V.

IOW, the safest course is definitely to reverse engineer the power circuit some but odds are you won't have a problem with 45-53V range straight from the battery array.

[Aalelan]

Re: PS for a Cisco AP

I don't have security torx drivers here at the house, just at the office.. I'll take it in Monday, crack it open, and see if I can makes heads or tails of things.. I have a wide range of skills but electrical circuit design is not in the list, I can build anything I have a schematic for, but to design something or try to figure it out might just be over my head..

But it was a freebie so if I do fry it by accident it wont hurt too bad. My netops buddy is back in the states now (we finally convinced the swiss to let us have him back) so maybe he as a spare PS and this is all not necessary too Thanks for the input, I'll let yall know what happens.

[Aalelan]

Re: PS for a Cisco AP

It looks like it has internal conditioning and such built in. but I was able to find a power supply today by asking the right people at the right time