RS-800 constantly switching to battery

[woody_apc]

This was originally posted on APC forums on 2/13/2011

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Hey everybody,

I've got a problem with my RS-800 (230V, 2004 model). At the beginning, an ethernet switch, an AP and a home server were connected to it, about 150 watts max in total. In spring 2009 I had to replace the batteries for the first time, in October 2010 I swapped the server, the access point and one switch, now totaling about 45 watts. Last December the UPS constantly dropped to battery (every 3-5 seconds). I saw strange fluctuations in the voltage displayed in PowerChute (sometimes dropping to 210V)...after having exchanged the power cord and checked voltage levels with appropriate equipment, I didn't know what else to do and set the sensitivity to medium - there wasn't a single drop in all those years due to fluctuations with high sensitivity and the narrowest voltage range possible before that. In fact, there was only one short power outage event recorded at all. About two weeks ago, the server had no power when I came home. Turning it on lead to immediate shutdown after booting up, so I disconnected the USB Cable and successfully connected remotely and changed the shutdown settings. The battery light was red, so i tried to do a battery test. Unfortunately, this lead to an instant power-off, so I was pretty sure the battery was completely broken. A 2A test load confirmed that one of the two 12V batteries dropped to 8V when loaded.
Although the UPS itself didn't try to switch to battery at that time, I unplugged it and connected in- and outlet cables directly.

Yesterday I got a new RBC32 and installed it, but the UPS is staying on battery while trying to switch to ac power about 3 times in two seconds in 5 second intervals. The power is completely spike-free and not fluctuating at all. Setting the sensitivity to low didn't solve the problem. Are there any chances my UPS isn't broken? And why does this happen after replacing the battery? I'd love to keep my UPS, but due to lack of power outages, I don't think I'd replace it if its broken. Especially when I can't rely on it and it causes more problems than it solves 😕

Thanks in advance,
woody

P.S.: A second UPS powering router, DSL modem, cable modem and telephone system in the basement is running just fine 😞

[juangele_apc]

This was originally posted on APC forums on 2/14/2011

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Hi Woody,

By any chance, since you have the software installed, have you tried changing Transfer Time thru the software and see if that will solve the problem.

[woody_apc]

This was originally posted on APC forums on 2/14/2011

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Thanks for your answer, but afaik the only way to change the transfer time is by setting the sensitivity? I'm already at low, whereas the second UPS (CS 650) is running fine at high (like mine did for 6 years), even if placed in the same room...

[woody_apc · Accepted solution]

This was originally posted on APC forums on 2/14/2011

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I'm pretty sure it's the UPS. I finally managed to get it "running" somehow, by setting the minimum voltage to 190V and plugging the power cord in and out a few times until the UPS stayed on AC. If the battery is fairly low and the UPS gets caught in the on/off intervall mentioned above, the minimum reported voltage is less than 200V, resulting in a kind of vicious circle. After dropping out of it, the reported input voltage is fluctating between 214-238V. Measured voltage is absolutely stable at 234.5V input and 234.4V output, ruling out some kind of contact issue inside the UPS. The CS650 reports 234V, without any change within the minute I kept an eye on the value.
At least it seems to be ok for now at low sensitivity, but this looks like a component inside the UPS is continuously degrading...a slow death 😞