[OT] Charging UPS batteries outside the UPS

[mike ledoux]

On Mon, Aug 06, 2007 at 10:10:30PM -0400, Ben Scott wrote:
>   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)?

Yes.

>   I've got an APC Smart-UPS 3000 (P/N SU3000RM3U) which I picked up
> for free (someone was getting rid of it).  It looks like it's in good
> condition, but it won't start[1].  I've checked the voltage on the
> battery, and it's less than 2 volts DC.  An aggravating quirk with

In that case, there is almost certainly at least one internal short
in the battery, and no amount of charging is likely to fix it.  It
takes some serious work to get a 12V battery down to 2V.

>   The battery consists of eight smaller units, wired together.  The
> wiring is easily disconnected.  Each unit is labeled "12 V, 7.2
> Ah/20HR".  Anyone if I can just hook each unit up to a regular
> automotive battery charger (one at a time) and charge them that way?

As others of mentioned, that depends on the battery chemistry.  Note
well that "sealed lead acid" doesn't necessarily mean "Gel".  It
could be an AGM battery, which will charge just fine with any decent
PbA battery charger.  OTOH, it sounds like the battery is already
pretty well fscked, so even if it is a Gel battery you aren't likely 
to make things worse (using a standard charger on a Gel battery will
not charge very well, and will certainly reduce the lifespan of the
battery, but it isn't likely to explode unless something else is wrong).

I have a few different chargers kicking around in my garage, I'd bet
at least one of them supports the charge mode your battery needs, if
you want to borrow one.

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