UPS observation

[mathog]

(Well, this is sort of a power supply.)

I have a couple of old omnismart Tripp-Lite UPS units (700PNP and 850PNP) which have been sitting unused for about 5 years. They were all functional when taken out of service. When plugged in one of them doesn't light up at all, and the other one lights up, but not surprisingly, the failed battery light is on. (And stays on, even if it is left plugged in for a couple of hours.) Now the funny thing was I had to clean out another group's storage area at work a few weeks ago and they had a couple of APC UPS units of about the same size. I don't know the history of those units, but there too one of them would light up when plugged in (and the failed battery light eventually went out, so I guess it charged up) and the other would not light up at all. Yes, reset the breaker on the unlit ones and it didn't make any difference.

Pretty sure in the 3 failure cases the internal lead acid batteries were dead (failure light) or good and dead (no lights), It seems unlikely to me that the electronics failed just sitting around. Do UPS units tend to stay dark if the battery is beyond hope? If so, how do they tell? (Detect a short, open, or something like that?) Yes, there were still batteries inside all of these units.

[severach]

Re: UPS observation

Unmaintained lead acid batteries discharge slowly at first. The lower the voltage the more damage the battery is doing to itself and the faster it dies and discharges. Expect batteries left alone for a long period of time to be completely dead with no hope of recovery.

Most soft power on UPS require some minimum voltage from the batteries to start up. The batteries are used to power the start-up circuits.

Almost all UPS require some battery power to function reliably. A running UPS with removed or completely dead batteries is unstable and may shut off and stay off with a temporary power fluctuation. Some brands destroy themselves when run with no batteries.

[kc8adu]

Re: UPS observation

the batteries rot in storage.its called sulphation.
well now you have mod fodder.
external batteries anyone?

[mathog]

Re: UPS observation

Most soft power on UPS require some minimum voltage from the batteries to start up. The batteries are used to power the start-up circuits.

Almost all UPS require some battery power to function reliably. A running UPS with removed or completely dead batteries is unstable and may shut off and stay off with a temporary power fluctuation. Some brands destroy themselves when run with no batteries.

That fits with what I saw.

There are lots of "desulfation" circuits on the web, including some that are just 120AC -> 100W light bulb -> bridge rectifier -> battery. That type at least seems like a pretty good bet for blowing up a sealed lead aid battery.

[b700029]

Re: UPS observation

That fits with what I saw.

There are lots of "desulfation" circuits on the web, including some that are just 120AC -> 100W light bulb -> bridge rectifier -> battery. That type at least seems like a pretty good bet for blowing up a sealed lead aid battery.

Those are mostly designed for open car batteries, where boiling the electrolyte isn't that big of a problem.