Green light but no battery power.

[Anonymous user]

Hi, 

recently I replaced the battery with a new one. And while plugged with power from the outlet, everything is fine. I get power from the battery side and the surge protection side. Green light is on, no beeping, no notification that anything is wrong (Note: PowerChute  not installed). We recently had a short blackout and to my surprise, everything shut down immediately on the battery side. On battery side, one monitor and one Dell XPS desktop was connected. Both in sleep mode.

I just retested this by purposely unplugging the UPS (with non-essentials plugged in) and it seems the battery had enough power for a second or two before everything went down on the battery side (and the surge protection side of course). Unfortunately one of the items was a hair dryer. Thinking that it may draw too much power, I redid the test with just a small desktop lamp on (a 15'' lamps) and a sleeping monitor. As soon as the UPS was disconnected to the wall outlet, the lamp immediately dimmed (half power?). With the lamp dimmed, UPS seems to provide power. Connected the computer to the battery side and turned it on. The computer seems to be in a continuous on/off/on/off/on/off/etc state as if it can never draw enough power to actually start loading (never even gets to the bios start or to the point where the dell symbol comes on). Computer actually sounded like a car having trouble turning on in the winter time. The UPS in the meanwhile seems to be in a normal "No power but providing power with no imminent battery depletion" state. I.e. beeps 4 times every 30 seconds or so. And this continues for a while (over minute). I turned off computer at this point as I didn't want to kill it somehow...and the UPS continues beeping 4 times every 30 seconds...

Is the battery no good? And if that's the case, shouldn't there be some kind of notification that it needs to be replaced? (note: the UPS battery has had days to charge so enough charge time is not the problem).

[Anonymous user]

Did the computer ever work with this uninterruptible power supply?

Your Back-UPS ES 750, like other popular UPS models, outputs a stepped square wave when operating from battery. Some computer power supplies cannot operate correctly from this sort of waveform, and will shutdown or cycle power very quickly.

If your lamp only dimmed slightly, that is likely due to the slightly lower output voltage of the inverter, and possibly also the differing wave shape as compared to utility power. You could try it with a different computer if you have one.

[Anonymous user · Accepted solution]

Hmm...the computer in question used to be connected to another UPS (Belkin something or other) which worked fine till the battery died and I connected to this APC one. This APC UPS on the other hand was connected to other Dell boxes and worked fine. So in that sense, this APC UPS has never been connected with this Dell box. I have another PC but it draws considerably more power though and currently connected to an APC Back-UPS Pro 1300. I can try testing the UPS with my other computer but will have to be later.