[OT] Charging UPS batteries outside the UPS

[VirginSnow at vfemail.net]

> Date: Mon, 6 Aug 2007 22:10:30 -0400
> From: "Ben Scott" <dragonhawk at gmail.com>

> Hi all,
> 
>   Off-topic but still techie question: Does anyone know anything about
> charging the batteries from a UPS using external equipment (i.e., not
> the charger built-in to the UPS)?

Most UPSs use gel cell batteries, which are basically lead acid
batteries in which the electrolyte has Ben gelled so that the gases
produced (H2 and O2) do not precipitate and no water needs to be
added.  Have a lookie at your batteries... are they completely sealed?
Do they have lead/cadmium hazmat designations?  (A lead marking would
indicate a gel cell, cadmium a NiCad, etc.  Most UPSs use gel cells.)

> It looks like it's in good condition, but it won't start[1].

That sounds like an idiot-proofing feature. :) FWIW, the APC UPSs come
with some kind of supposedly super sophisticated warranty.  Do you
think APC could help you as a last resort?

>   Now, I don't want to have to spend $350 on a replacement battery
> only to find out that it's the UPS itself that's shot.

You can pick up gel cells at your local Radio Slut^H^H^Hhack under the
term "alarm battery" because they're used as battery backup for
security systems.  You're probably looking at more like $100 for an
appropriate battery replacement solution though.  So don't even think
about paying $350 for a replacement battery...

>   The battery consists of eight smaller units, wired together.  The
> wiring is easily disconnected.  Each unit is labeled "12 V, 7.2
> Ah/20HR".

First, confirm that these batteries are wired IN PARALLEL, NOT IN
SERIES.  (If they are in series, you're looking at a highly
non-standard 96V implementation.  No problem, though... just
disconnect them all and charge them separately.)

> Anyone if I can just hook each unit up to a regular automotive
> battery charger (one at a time) and charge them that way?

You should be able to hook each of the batteries (or all of them IF
they're wired IN PARALLEL) to a standard 12V battery charger WHICH HAS
A GEL CELL CHARGING MODE.  NB that last part!  Gel cells require a
different current/time charging profile than other types of batteries.
(IIRC, http://en.wikipedia.org/wiki/Gel_cell describes why.)  Hooking
your gel cells up to a "standard" 12V battery charger (one NOT
designed for gel cells) CAN DESTROY THE BATTERIES!

> in a UPS without a battery; loose battery connector indication; what
> if the customer is stupid and didn't connect the battery.

IIRC, APC UPSs (how's that for an acronym?) generally ship with the
batteries DISCONNECTED.  When you get it and first open the box, the
instructions tell you how to hook them up.