APC Fault

Ian Bannister Member

Hi, I have an APC UPS RS800 and it has stopped working. After a short while it alternates between the "Online" and "on battery" lights and clicks as it changes from one to the other. What can be wrong?

Ian Bannister, 2025-02-13 13:32:53 +00:00

#122

NB-23 Member Warrington

Howdy
we'd need to check it here, but it could just be doing its job and responding to poor power. Do you have it on a generator or unrelaiable source feed?

NB-23, 2025-02-20 12:54:32 +00:00

#124

Ian Bannister Member

No, it's plugged into my normal ground floor 240v socket. It worked fine for a couple of years but then developed this fault. I've taken all the feeds off but it still has this problem.

Ian Bannister, 2025-02-20 19:52:24 +00:00

#125

NB-23 Member Warrington

How old are the cells? If replaced within the last 12 months we can explore finding a UPS that uses the same. I dont think its economical to look into this one as its relativley low value.

NB-23, 2025-02-21 10:11:18 +00:00

#126

Rob Beech Member

Did you ever get to the bottom of this? i have 2 of these that have started doing this. (New cells don't fix it). They'll run on battery but will switch to mains and immediately back to battery. Mains is absolutely fine. Not really worth spending too much tme over as they're not expensive but if there was a common fault on a board that was known about i could look to fix in house.

Rob Beech, 2026-02-23 14:12:11 +00:00

#156

NB-23 Member Warrington

Hi

the unit was not sent back. Either the customer found the solution or moved on.

When you say mains is fine - you'd really need to be sure. Pragmatically this could mean having more than one UPS of the same type to compare behaviour, but even then there are differences between parts due to component tolerances.

NB-23, 2026-02-23 14:17:05 +00:00

#157

Rob Beech Member

We have 10 of these, the others work ok, these 2 have just started doing this recently (but not at the same time). They do "run" ok whilst they're doing it, just with the double click (one way then the other) every 4 or 5 seconds and sometimes the ocassional short beep and flicker of the overload light (but the current draw is between 250mA and 500mA so not overloaded). We've taken them out of service as we're not sure what the consequences of the constant switching could be whilst unattended.
Realistcally they're old and i'm more than happy to consider them scrap but if there was a known "it'll be this component on this board" type solution we have facilities to replace that here so would be a quick fix.

Rob Beech, 2026-02-23 14:24:37 +00:00

#158

NB-23 Member Warrington

This solution is pragmatic and to sum up though they still work, its not worth the risk keeping them in service. If you have the option consider running one on your desktop machine to see if you can get correlation to anything else.

The overload light flashing ... I dont think there is an overload light on these - probably the on battery light, which if when it illuminates is accompanied by continuous alarm indicates an overload. Makes things trickier.

User guide is here
https://secure.ups-trader.co.uk/index.php?controller=attachment&id_attachment=304

NB-23, 2026-02-23 16:36:52 +00:00

#159