[Coco] Off-topic question for electronics wizards

[Gene Heskett]

On Saturday 28 February 2015 15:02:00 Christopher Barnett Fox wrote:
> Hey folks,
>
> Sorry to send out an off-topic message, but it does relate to
> electronics, so perhaps not entirely off the mark. I have a pretty
> basic question that could probably be answered very quickly by someone
> with enough background, and this list seems to have ample supply. I
> confess while I'm very interested and willing to learn, I'm an
> electronics amateur.
>
> My Verizon FiOS ONT backup battery, a GS Portalac PX12072 SLA, needs
> to be replaced. This is a 12V 7.2Ah battery, used only to maintain
> voice services in the event of a power outage. I do not have Verizon
> land-line service (or any land-line service, for that matter), and
> only use Verizon's FiOS broadband internet. The BBU doesn't provide
> any backup supply for data services.
>
> So, I don't want to spend the ~$20 to replace the battery, but the
> darn ONT won't stop complaining about the missing/presumed dead
> battery, with an obnoxious BEEP every five minutes or so.

How old is this battery?  Nicads have about a 200-500 recharge cycles in 
them, but will grow metal whiskers and short out internally in 6 months 
or less if left on a trickle charge.  Lithiums hold a charge much 
better, and I personally have not yet had a failure in my power tools.

But if its a gel-cel, a lead acid IOW, they'll typically have a working 
life of 2 to 4 years depending on how smart the charger is.
> Here's my line of thinking... could I "trick" the ONT's battery backup
> unit into *thinking* it has a fully-charged battery by just using a
> 120V AC to 12V DC transformer? I have loads of spare "wall wart"
> supplies around, and I'm sure I could scrounge one up that provides
> 12V DC. Does the output amperage matter?

Generally a bad idea IMO.  If the battery is sulfated, the voltage will 
rise  to 16 to 18 volts, and that wouldn't be healthy for the rest of 
the device.  If its got a shorted cell, then the voltage will for a 
short period of time, be held to under 11 volts, probably overloading 
the wall wart to the point its internal thermal fuse will clear, usually 
before it starts a fire..

If its 2+ years old, in lead acid terms it doesn't owe you a thing, 
replace it. I have a couple 12 volt LA batteries sitting on the floor, 
to go into my UPS yet tonight as the nearly 5 yo batteries in it signed 
off a while back.  At a tad over $40 in the front door, those new 
batteries will replace the dead ones, and I owe the old ones a decent 
recycling.

The key word here is TANSTAAFL.  As said by a C.E.T. ;-)  Plagerized from 
E. Hemingway by way of R. A. Heinlein. :)

> Thanks for your time and expertise!
>
> Christopher

Cheers, Gene Heskett
-- 
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