On Wed, 4 Dec 2019 03:39:34 +0000 (UTC), danny burstein
wrote:

In Clare Snyder writes:

The battery on my Sola 450 on the downstairs TV just went south so
it's riding bareback at the moment.

For the hell of it, try hooking up a 12V low amperage battery charger
to the bad battery.
The battery reads 13.8 volts as removed from the UPS. Won't light a
10 watt bulb for 5 minutes - a good battery will light it for 4 or 5
hours. By the way, the battery is AT LEAST 8 years old - - -

UPS'es will often not charge the battery at all if the voltage
has dropped below (something like) 8V.
It's not a problem with taking a charge - it's a problem with
supporting the load. A GOOD UPS does a self-check every once in a
while - and if the battery does not meet spec it alarms.
I've sold (and serviced) hundreds of UPS units from cheap 250 va
standby units to very expensive 3KVA online units for over 25 years.
ANd I have yet to run across a UPS that would not attempt to charge a
dead battery. It might not produce a high enough voltage to force a
charge into a BAD battery - but eventually it WILL recharge a dead
GOOD one

For that matter, "smart chargers" like the Battery Tender brandname
unit won't, either.
Virtually no battery charger with reverse connection protection will
charge a dead battery. I have often used my lab power supply to
"kickstart" dead batteries.

I've found that a good chunk of UPS'es with "dead batteries" will
work [a] if I take out the battery and dumb charge it a bit.

[a] by "work" I mean get a modest amount of run time from them.
Don't count on full cycling...
Don't count on them supporting hald the rated load either.