Problem with UPS

I don't have your exact UPS, but most charge up the batteries whenever the AC is turned on and use those charged batteries when the AC fails. It sounds like your charging circuit is not functioning. Depending upon how knowledgeable you are about electronics, you might see if you can find a failure in that circuit. The first thing I would look for would be to determine if a charge voltage is being applied to the battery when AC is on. If that was OK, next I would look for a diode used for isolation of the charged battery. It could be you are discharging the battery through such a shorted diode. Of course it could be MANY other things. On the other hand, it might be better to buy a new unit.

It looks like the old battery shorted some cells and took away some fuse or protective resistor in the charging circuit. It might even be removeable without soldering.

By the way when the 7 Ah battery on my UPS failed I replaced it with a

96 Ah car start> Hi - wondering if anyone can point me in the right direction with this one.

"P" wrote in message news:newscache$j1k3fj$ip2$ snipped-for-privacy@goliath.homenetwork.tenretni...

That's very similar to the problem I have with my APC Smart-UPS 700, and like yours, it seemed to occur after a worn out battery was replaced. The problem happens intermittently on mine, after it performs one of its periodic self checks. It's not "bad joint intermittent" - more "I'll let you down just for the hell of it" intermittent. Prior to it failing, all front panel indications are normal. After failure, it indicates low state of charge, and faulty battery. This is after it has attempted to power the load ( and failed I might add ) as part of the self check. About the only thing that I have come up with, is that it's a battery terminal issue. The reason that I say this is that the original batteries ( there's 2 of them in mine ) had quarter inch terminals, with suitably matching spade connectors on the battery to battery jumper, and the main leads into the rest of the device. The replacement batteries, which were obtained for me by a friend, so not negotiable ( !! ), had the smaller terminals, so the original spades did not fit as well as they should. When these things go into load-power mode, the current drawn from the batteries is very large indeed, and it might just be that these connections are poor enough that under these conditions, as opposed to when the thing is just idling and trickle charging, there is sufficient voltage drop across the connections, for the system control micro to decide that the battery is faulty. It could of course be that one of the 'new' - remember my friend got them, but they are supposed to be new ... - batteries is genuinely faulty. It's a case now of having the time and inclination to take the thing out of service again, to check it all.

Arfa