[OT] Charging UPS batteries outside the UPS

Ben Scott dragonhawk at gmail.com
Tue Aug 7 10:13:11 EDT 2007


  This is an amalgamated reply.  Thanks for all the responses,
everyone, it's been informative and educational, as always.  :)

On 8/7/07, VirginSnow at vfemail.net <VirginSnow at vfemail.net> wrote:
> Most UPSs use gel cell batteries ...

  These are gel cells.  So-called "sealed lead-acid".

On 8/7/07, Jim Kuzdrall <gnhlug at intrel.com> wrote:
> My auxiliary charger ... (You are welcome to use it - I will email it to you.)

  Rather than emailing the charger, just hook it up to your computer,
and use an SSH tunnel to transmit the charging current to me.  ;-)

On 8/7/07, Jim Kuzdrall <gnhlug at intrel.com> wrote:
> It is safe to recharge them with a conventional automotive battery
> charger as you suggest.  ... If anything goes wrong, they will just
> get hot or not take a charge.

On 8/7/07, VirginSnow at vfemail.net <VirginSnow at vfemail.net> wrote:
> Gel cells require a different current/time charging profile than
> other types of batteries. ... a "standard" 12V battery charger ...
> CAN DESTROY THE BATTERIES!

  Hmmmm.  So much for an easy answer.  :-)

  http://en.wikipedia.org/wiki/Gel_battery doesn't really give much of
a clue, other than to say "Charging with a constant voltage ... can
cause a rapid initial current", which doesn't really help me much.
Does that just mean it doesn't work as well, or that it is
don't-cross-the-streams-bad?

  Still, maybe I can find a charger that has a "gel" switch on it somewhere...

  On the third hand, the batteries are useless anyway, so maybe I'll
just hook 'em up to what I've got available and see what happens.
Outside, away from anything combustible, and in a pan.  :)

On 8/7/07, VirginSnow at vfemail.net <VirginSnow at vfemail.net> wrote:
> First, confirm that these batteries are wired IN PARALLEL, NOT IN
> SERIES.

  The battery in this unit consists of two packs of four units each.
In each pack, two pairs of units are wired in series, and the pairs
are then wired in parallel (within the pack).  The wiring in the UPS
connects the packs in series.  So, the units are 12 V, the packs 24 V,
and the whole battery is 48 V.

  Keep in mind this is a 2250 watt, 3000 VA UPS.  The battery is
bigger than what you would find in something at Circuit City... :)

  With regard to replacement batteries:

  I'm aware of pricing and OEM vs third-party and so on.  The $350 was
a rough number, partly hyperbole, and also reflected S/H (they are
rather heavy).  Even if I can find a replacement for $CHEAPER, that's
still more than I want to spend on a potentially dead UPS.  :-)

On 8/7/07, Jim Kuzdrall <gnhlug at intrel.com> wrote:
>> [4] Severe discharge typically also means the battery will
>> not hold a load to spec ...
>
> Actually, when lead-acid batteries lose capacity after many partial
> discharges, the recommendation is to have a "deep discharge" and
> complete recharge.

  Like I said, I find APC's explanation rather suspect.  Aside from
technical concerns, they have a Conflict Of Interest (selling me new
batteries).

On 8/7/07, VirginSnow at vfemail.net <VirginSnow at vfemail.net> wrote:
> FWIW, the APC UPSs come with some kind of supposedly super
> sophisticated warranty.

  I suspect you're thinking of the "equipment protection" stuff, where
APC will pay to replace any equipment the UPS failed to protect from
damage due to a power transient.  The warranty on the UPSes themselves
are fairly standard (some number of years).  They do pay shipping both
ways.  Dead batteries are not covered, though.  And I believe this
unit is out-of-warranty.  Either way, if I call support, they'll just
tell me to replace the batteries first (not an unreasonable stance,
given the situation).

-- Ben


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