Hi!

IME, when the batteries are toast, you won't get *any* up-time
from the UPS. *Power goes... and so does the UPS! *:-/

I guess I consider them toast when the UPS still holds the load, it
just holds it for a few seconds or minutes--or it visibly struggles to
keep things going. (Meaning the output voltage sags to the point where
equipment won't work. Most don't do that, but some do.)

I've seen lots of UPS's discarded because they have killed
their battery packs. *Bulging battery cases, cracks, etc.

Most of the ones I see aren't that catastrophic. Perhaps that comes
from not realizing that they have failed and leaving them plugged in
for ages, presumably trying to charge batteries that simply cannot do
any more. Apart from a few Tripp-Lite units, the worst I've seen is
one or more cells that simply ran out of liquid. Very few units that I
come into contact with use gel-cell batteries.

In fact, the only one that I ever saw one that did was a really big
old Tripp-Lite monster that went "bang!" every time it powered on and
that put off an even bigger BANG and smoke when something inside blew
up.

Some UPS's actually power the load continuously and are
recharging the battery from the AC line (like telco's operate).
I would think this would be more stressful on the switching
power supply than the battery (as, essentially, the same current
is flowing into the battery as out)

I suppose it is, and that means the inverter itself must be built well
enough to stand a high load and constant operation.

I've also previously discarded a Back UPS 600 (?) as it used
a different physical size battery that was hard to come by
(since it didn't offer any feature that I didn't have on other
UPS's -- and, also had two pigtail power outlets on the
rear which always seemed like a kludge).

I have some similar units that got lawn tractor batteries as
replacements. By all indications they work fine.

I managed to blow up another larger UPS (3KVA... the size of
a dishwasher) by forgetting that power was still available
from the battery pack even though the AC mains were
disconnected... shorting a 120V battery into damn near anything
destroys the "anything"! *: )


HeHeHe...and it probably puts off a nice bang, some ozone and "a bit"
of a spot weld on the shorting object--when and if it ever comes back
down to earth.

The biggest UPS that I've had personally was an ancient APC 1200VA
unit. It seemed to be pretty well protected with massive sand fuses
between the batteries and inverter, and large circuit breakers on the
output side. I once hooked it up to some car batteries (the biggest
ones I had sitting around) and abused it a little bit by hooking up a
moderately sized 110 volt room air conditioner.

It struggled to start the A/C but once it was running, everything was
fine. I just had to try it. More than once the UPS just gave up and
quietly shut down.

It still worked when I sent it off for recycling. I just didn't need
it and had nowhere to put the batteries. It hummed almost like a
microwave whenever it kicked on and had an impressive inverter inside
it.

All of my UPS's are connected to PC's or servers. *So, all feed
reactive loads. *Most are oversized for the loads they power.
Occasionally, I will run an extension cord from one of them to
power a CF light in another room if we have an outage at night.
(a "100 equivalent watt" CF runs for a LONG TIME on a small UPS!)

I ought to get that going again. I rigged up a very nice power outage
lighting system for my basement with an old APC UPS and a BIG gel cell
battery. (The battery got snaked from work after the Tripp Lite UPS
blew up. It was basically new and fit nothing else they had, so it was
either that or they would have trashed both of them.)

I should have used CFL bulbs at the time and didn't. I also never
added a relay to make the lights go on when power went off--they had
to be manually operated or on all the time.


All of the APCC devices have "replace battery" indicators.
All of them do a loaded test on power up (for about 2-3 seconds).

It's not a very good test and won't spot a faulty battery unless it is
REALLY bad. The particular 1200VA UPS I mentioned above would pass its
self test on the completely exhausted internal batteries every time.
Yet if you pulled the plug, it went down, not across.

I think all of the APCC designs use low voltage primaries. *E.g.,
12 or 24V. *I don't know if the battery abuse is consequential
to this (perhaps the charging circuits on the UPS's that I've
had that utilized 48V or 120V primaries were better designed
of necessity?)

That's what I've seen on the smaller models that come in capacities up
to 1500VA--which covers pretty much all the Back UPS series. These
also have modified sine wave inverters.

The bigger ones (Smart UPS 750XL and bigger) all seem to use 48 volt
battery arrangements (four twelve volt batteries) and most have true
sine wave inverters. They also have forced air cooling.

I've taken to powering the UPS's off when their loads are not
in use.

That really could only happen on a UPS where the load is supported by
the inverter all the time. If there is good line power on a
traditional line-interactive UPS (a relay closes and energizes the
inverter when the lights go out) it won't use the battery for
anything.

Most designs also charge the battery whenever they are plugged in. A
few (most notably the cheap APC "plugstrip" UPS units will *drain*
their battery even when turned "off" and unplugged. I guess this is
because the power switch is "soft" and doesn't shut the
microcontroller down.

(it also has the advantage of silencing the silly alarms that signal
in the event of a power outage -- if the UPS is on but its loads
are NOT, then I really don't want to be bothered by a chorus of half
a dozen little "chirpers"!)

Heh. I usually remove the beepers from the units I buy when I get
them. I don't want to hear them for any reason, and telling the
bundled control software to turn the speaker off usually won't make it
quiet all the time (it would still come on if the battery were nearly
depleted or bad) and you've got to install it.

So I just yank 'em with a quick touch from the desoldering iron.

I don't think it prudent to use regular lead acid batteries
("car batteries") in these applications unless the batteries
themselves could be located in a ventilated area -- I'd be
wary of outgassing.

I've done it and never had a problem. Any room that's decently
trafficked or serviced by an air handler (or furnace) should move
enough air to dissipate whatever gas might show up. I've also never
noticed the characteristic smell of the gas building up near the
batteries when they were in use.

However, I did take some precautions with the ones that I have here.
Most notably, they are in a breathable container with a lid and
openings that would be unlikely to spew nasty stuff even if the
battery went off.

To my knowledge, all lead acid batteries are vented somehow, so even
the ones that came in your UPS will release some gas if they have to.

William