RB532 on UPS locks up after AC power loss?

Hardware MikroTik hardware general
1

This has happened three times now, after the 2nd time we replaced the RB532 with another thinking that it was perhaps a bad board.

In all case AC power was lost, and the system ran for an unknown period of time on the battery backup. At some point while on battery, the RB532 hard locks and must be physically power cycled to be returned to service (even after AC power is restored).

We are powering the unit with a POE48v power supply, connected to a very very small APC brand UPS. Something like 250VA, but it’s only powering the RB532 w/ SR2 and 2511MP cards. I estimate the UPS run-time is a few hours, something like 6 to 10, perhaps less. I was not able to do an extensive run-time test before deploying the hardware.

I did see this post on the routerboard forum talking about how the board can lock up when it goes under 10V. Is this true?

My speculation is that as the battery backup gets low, the POE48V’s output voltage is reduced to the point that the board goes under-power and enters the “feedback mode” the poster on the routerboard forum talks about.

I am certainly no electrical engineer and do not have the knowledge, tools, or skills to test this theory. What do ya’ll make of it?

2

The AC voltage from the UPS will stay somewhat constant until shutdown. But the waveform on a “cheap” UPS might change and have an effect on a switching 48 supply.

We use the same setup with several other products (not MT…yet) without issues with the larger analog brick type supplies.

If you pull the UPS plug does the PS you are using raise in temperature?

First thoughts and two cents,

Mike

3

If you’re just powering the RB, check out one of these UPSs:
http://www.apc.com/products/family/index.cfm?id=133

Basically a DC powersupply with battery and charger. Should be better than an AC UPS in terms of runtime and behavior for what is ultimately a DC load. I bought from PC Connection for $100ish.