snip


I work for a major battery manufacturer and also have worked on my share
of
UPS's over the years...so I feel qualified to answer your question.

The answer is not as clear cut as you might imagine.

Since the charger is designed to charge a smaller battery
there is of course the possibility the batteries may not charge fully...
however a problem might only occur is there was a very long power
failure
and the batteries got deeply discharged.

The real danger is in the emission of hydrogen gas...which of course is
explosive!

The battery that's in the UPS now should be a VRLA battery.
That stands for valve-regulated lead-acid. It's designed to allow a
negligible amount
of hydrogen gas emission under all but a thermal run-away condition.

The deep-cycle batteries you have, could be the "wet" type which would
emit
hydrogen
and could therefore be potentially dangerous.
Since VLRA deep cycle batteries do exist the ones you have *might* be
safe
to use...but be sure to
find out if they are the "wet" type (with liquid acid inside) or
"sealed"
VLRA's

The VLRA is a fairly expensive battery and can cost over $200 each!

The good news, is that since the charger is going to be undersized for
the
batteries
the chances of a dangerous emission of hydrogen is minimized...but that
is
not to say it would be safe.

Since you will be using the deep cycle batteries in the summer
(presumably
in your boat)
you are going to have to replace the internal battery anyway...
So you might as well not bother with the deep-cycle batteries you have.

When in doubt err on the side of caution.


Thanks for the info. The deep cycle batteries are the wet type. I would
bet
neither would need any charging from the UPS all winter as you say,
especially if hooked up in parallel. I use the UPS almost exclusively only
for the voltage-leveling attributes, not document preserving -- if they
keep
my automatic bilge pump going all summer, they would probably only need
the
usual amount of monitoring over winter.

If I decide to try it I will take care to provide plenty of venting.

Once I got the jumpers in place I could forsee even using one of my handy
portable 12V jump-start power packs for backup as well -- they are VLRA
types.






Considering the batteries will be a much higher Ampere-Hour than the
charger,
the amount of gassing will be negligible...but I just wanted to sure you
were fully cautioned.

Basically, no smoking or flames near the batteries!

BTW: There are several possible charging methods...but if the voltage
remains below 14.2 volts while on charge,
the gassing is next to nothing.


I see I also made a few typos, valve regulated lead acid is VRLA G