Help - UPS not charging

I have a UPS about 11 years old. It is an IBM OfficePro 700 which is actually a Tripp-Lite product. Inside on the circuit board it says

66-0546. The web says the Mfr model number is 10K1912.

Not too long ago its yellow light started flashing that says the batteries are discharged. Because of its age, I assumed the batteries were worn out so I bought new ones. Unfortunately, after installing them the problem did not go away.

When plugged in to AC, the unit has its green LED lit which shows it is getting AC power in. The yellow LED flashes. according to the manual, "This yellow light will turn ON continuously to indicate that the UPS's battery is less than fully charged. If it stays on continuously, contact Tripp-Lite fo service. The light will flash after you set the 'OFF/ON' Switch to the 'OFF' position to indicate that the UPS will not provide battery backup during a blackout or brownout." Regardless of whether I set the OFF/ON switch to OFF or ON, the yellow light flashes.

There is a Mute/Test switch. If I run the test, the red LED briefly lights and the alram briefly sounds, as if it tried to switch over to battery power but there was no power there.

It kind of seems like the charging circuit is not charging the batteries but I don't know how to test this theory. I left it sit plugged in for a few days hoping it would charge but it did not.

There are several fuses on the circuit board, all soldered on, and they all measure zero ohms so I don't think that is the problem. There are no obviously leaky capacitors or any other components that look burned up or damaged judging by visual inspection.

I like this UPS and would like to revive it, especially since I spent money on the new batteries. If anybody could help me diagnose the problem, tell me where to start, what to check, etc. I would appreciate it.

All ideas welcome. Thanks in advance.

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The batteries should have come with enough charge to operate the unit or at least pass the battery test. Make sure the connections are correct.

Live Fast, Die Young and Leave a Pretty Corpse
Reply to
Meat Plow


Thank you for the reply.

The connections are good. When any of the battery connections are disconnected, I get no lights at all on the front panel. Right now I have it torn apart enough where I can see all the connections. I have all connections oriented the same as the batteries I took out. The (2 x 6V) batteries are connected in a series and currently measure approx. 13.2V total. Thanks.

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I know it's no consolation (or help with your problem now) but any time a cheap (i.e."desktop/office") UPS shows symptoms of failure the battery system is the culprit 95% of the time, or more.

When it IS a genuine UPS fault, it is almost always beter to junk it and buy a new one.

The only way you can tell which is the fault is to jury-rig another battery to the UPS and see if the symptoms continue. Fortunately most of this category of UPS use 12V so a spare auto battery will suffice.

(I have a bank of four 12V >100Ah SLA's which I am routinely using to verify the functionality of assorted UPS' brought here, up to ~6kVA.)

Reply to
who where

From your description it appears that the light is flashing, whereas if the UPS considered the batteries insufficiently charged, the light would be constantly on.

I'd check the continuity and connections to the on/off switch, given that your manual effectively says that the flashing light means that the switch is in the off position. Make sure the switch continuity actually changes state, and determine whether it's closed in the "on" position, or vice-versa (the latter seems unlikely, but best not to assume). Try to track the connections from that switch back to whatever is looking at it - probably an IC - could just be a dry joint, or a short, depending on how the switch is used. If you can track back to an IC pin, you can check whether it changes state - with suitable care given that you'll need the battery connected, and this device might start generating mains voltages at any moment.


Reply to
Sylvia Else


Monitor the battery voltage with the unit unplugged from the 120V wall/ floor outlet. Then plug it in and turn it on. If there is any charging going to the batteries, the voltage should show some sort of an increase, say from 13.2 to 13.5V, at a minimum. Most lead-acid 12V or 2 x 6V batteries should go up to around 14V when charging at a medium to high rate. If you don't see the increase in voltage, then you must check out the charging circuit. Have you contacted the manufacturer and asked for a circuit diagram. That should really be your first move.

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THANKS, Sylvia, and thanks to each of you who took the time to try to help me.

Good call on the flashing light =3D unit off =3D bad switch. Problem solved.

It looks like a typical SPDT slide switch. As I was preparing a state table of the switch leads to show you all, I thought how unusual it was that the continuity toggled normally between the "left" and center poles when the switch was moved, but between the "right" and center poles it was always open. So I started monkeying around with the switch and sure enough, at one point I got it just right and got continuity between the "right" and center. I hooked everything up and got a green AC indicator with no flashing yellow, just like we wanted. I plugged in a small load and killed the input power and voila, battery backup!

I flipped the switch back and forth a bunch of times and now it actually seems to be working pretty consistently, so at least for the time being I'm not even going to replace it. If it screws up again it will be first on the hit list.

I'm glad it turned out to be the switch because the way the board and components are laid out, I was getting nowhere on tracking the connections from the switch.

This solved two problems for me:

1) The dead UPS.

2) The dead UPS has been in pieces on my kitchen table since October and I have parts for a new PC hopefully coming tomorrow, so I needed to make room for that project.



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