Question about APC Back-UPS® XS 900 (BX900R) UPS System
I bought an APC 900XS UPS for $10.00. at a garage sale. I know you’re going to tell me that you take a gamble at a garage sale whether it works or not.
Please do not try to fix the device unless you are qualified electronic technician. There is high voltage and high current that is very deadly.
Before plugging the UPS in I opened the battery compartment and found the positive lead off of the battery. Took the batteries out and measured the voltage on both batteries and I couldn’t believe it, they were both good. Well at least they measured the right voltage. There are two batteries, each one is 12vdc. The real test would be to put the batteries under a load.
I plugged it in and ran for about six hours than the "Overload" LED and alarm turned on. I didn't have anything plugged into it "AC". When I first plugged it in, in the beginning I noticed the fan was running by the sound of it. But later that evening about an hour after plugging it in the fan was off. Don’t know why unless there is a temperature monitoring circuit on that heat sink and the fan wasn’t needed? After opening the unit I found a component unsoldered at one end. It looks like a capacitor or a spark gap component across the AC line. I don’t think that’s original problem. Re-soldered the component back in place. Took the board completely out and unplugged all the connectors. Again, after talking the PCB out. I didn’t see anything damage / burned. Without a schematic diagram one really can’t troubleshoot. I did noticed that (small) fan was kind-a hard to move by hand. I applied an external 24 volts to the fan. It was almost drawing 0.120 amps. The fan is rated at 0.070 amps. Took the fan apart and applied Tri-Flow (oil) to both bearings. Now the current draw has lowered. I’m wondering if the PCB has a current monitor of the fan driver, if the fan is/or requiring too much current that the unit shuts down. That heat sink that the fan is on seems to not dissipate very much heat, if any. It seems the fan is an over kill. There is a temperatures sensor mounted to the heat sink, probably to monitor the temperature of the heat sink in case the fan stops. Temporally connected everything back together. Now it’s running fine, but time will tell whether it’s going to stay running. After running four hours without any alarms, I re-assembled the unit. It’s been two days and the fan is still running and without any alarms. I haven’t plugged the computer into it yet.
Posted on May 11, 2010
Did you open up the battery compartment and connect the battery leads correctly? (At least once, I managed to get the lead that shipped in place to come loose as I put the battery back in to the compartment.) Then let the unit charge (while off for ~16 hours).Make sure you do not have equipment that takes more than 540 watts plugged in (many gaming systems have larger power supplies than this). That is the rated full load for this UPS..
If you have done all of the above, contact APC because you have a faulty unit.
I hope this helps.
Posted on Dec 09, 2009
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Posted on Jan 02, 2017
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