Back-UPS 650 boots to "sleep mode" after replacing battery. Functions as inverter, but not as UPS.

[Anonymous user]

Hi All,

I replaced the battery in my Back-UPS 650 (Model #BK650MC).

Now when I power up the UPS it goes directly to sleep mode, beeping once every 4 seconds.

If I depress the rocker switch in the direction of the "no alarm" icon, the UPS turns on and supplies power perfectly. But it will not go "off battery" after that. I thought maybe for some reason it's not sensing the line voltage? So I tried this in several different outlets. I've tried it with the unit plugged in first, and with plugging the unit in after the battery is supplying power to the outlets. Neither way will kick the unit out of backup mode.

There are microswitches in the back, but a.) I don't think they got switched somehow and b.) I don't quite understand what they do (nor have I been able to find any documentation on them). Not sure if there's a possible fix there or not?

When I press "test" on the rocker switch (by rocking it away from the "no alarm" icon) nothing happens.

Does anybody know why this might happen?

Is it possible the unit somehow become damaged when the last battery died (doesn't seem likely)?

Again, it functions perfectly as an inverter. But not as a UPS, at the moment.

Any info/ideas/help greatly appreciated.

Thank you,

Bud

[Anonymous user]

Hi Jon,

Thank you for your reply and for the manual that has the "option switch" settings listed in it. I traced things out in the order implied by your response. The main breaker was fine. The UPS is well-past warranty so I didn't mind opening it up to check the internal fuses. Indeed fuse F3--1A 125 volts--is reading infinity.

Any idea who the most likely downstream  culprit is that caused it to blow?

In the meantime I'll check my stash to see what I have for fuses. I believe I just came across some of these the other night.

Peace,

Bud

[Anonymous user · Accepted solution]

Hi Jon,

Thank you for answering. It's an APC battery, but one with fewer amp-hours, which I don't think should be a concern. Also, the battery cirucuit appears to be working fine as the unit will operate as an inverter (just not as a UPS).

I replaced F3 today and it blows immediately upon plugging the unit in. 

I wonder if the fuse was placed there to protect the unit from a sticking relay? I ask because that's where the F3 fuse connects.

I'll have a closer look at things later.

I'll update here to help anybody who might have a similar issue in the future.

Thank you for your help,

Bud