BVN650M1 worked for several years, now only works in GFI outlet

[Bart_Z_Lederman]

This is one of the stranger things I've seen.  A few years ago a friend bought a BVN650M1 to protect his computer.  A week or so ago it started the "screaming" and flashing lights which others have seen.  I took it home to see if I could do anything with it.  It worked fine in the first outlet I plugged it into, but when I tried a different outlet next to my computer it went into 'scream' mode.  When I put it back into the first outlet, it worked fine.  After a few more experiments, I found that the unit will work fine IF it is plugged into a GFI protected outlet, but not in any regular outlet.  The wireing in my outlet is fine, and two other UPSs of my own work just fine in the same outlets.  It appears that something has gone wrong inside the unit that makes it sensitive to power input.  Does anyone have any ideas, and can this model even be opened and repaired?

[Teken]

You’ll need to be more descriptive as to the sound the unit makes.

ie: Continuous Tone vs Pulsing Tone / LED indicators.

When the unit is making a tone check the building wiring fault indicator light on the side. If it’s lit (red) this indicates a building wiring fault.

This can be from bad ground, voltage on the neutral, loose connection at the outlet / breaker, high resistance Earth ground, improper bonding etc.

If no building wiring fault LED is seen but the tone is continuous this indicates the following: Battery disconnected, battery expired, over load while on battery only power, internal fault.

I have appended the user manual for this specific model APC UPS:

https://download.schneider-electric.com/files?p_enDocType=User+guide&p_File_Name=BU+UM+990-6275+MN01...

Call out what behaviour is seen and compare it to the fault indicators in the manual.

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[Bart_Z_Lederman]

After doing more testing, I think the primary problem is that the unit was discharged. The friend I'm helping isn't very technologically savvy, and might have unplugged the unit.  I plugged it into a GFI outlet and let it charge overnight, then left it turned on as I moved the plug from a GFI outlet to a normal outlet and let it sit for another day.  It now works properly if I turn it off and then turn it on again while plugged in to a normal outlet, or with the unit unplugged.

This still does not explain why the UPS would not recharge from a normal outlet.  As I mentioned in the beginning, I have two other UPSs of my own: a BN900M and an SE450G1, and neither of them have ever reported any wiring faults.  I also have a piece of test equipment specifically designed to test power outlets: it plugs in and lights show if there are any problems.  I can state with an extremely high level of confidence that there are no wiring problems in my apartment.  In addition, the unit behaved exactly the same way when I first tried it in my friend's apartment 45 miles away connected to a different power company.

Since the UPS now seems to be working the problem is not urgent, but I think it is worth trying to find out why it works this way.  I have not tried to run down the unit with a load while unplugged, but I'm willing to try the experiment if anyone thinks that would be useful.

[Teken]

The behaviour you’re describing about why it didn’t recharge is a common design problem in this UPS and others. 

It has nothing to do with it being on a specific outlet whether GFCI / Standard. Depending upon model APC UPS the system must detect a minimum battery voltage.

If the expected voltage is not seen the unit will not power up with the button. In concert depending upon the firmware loaded in the unit it will also (NOT) charge the battery cartridge regardless if it’s on / off.

The vast majority of APC UPS will by default charge a cell when AC Mains is connected. It’s at what battery voltage that it won’t and that’s to offer a measure of safety & protection.

If a cell is shorted or completely flat the chances of a uncontrolled explosion is extremely high upon charging. As the cell will heat up very quickly and either begin to vent, deform, or cra ck open.

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