[PLUG] experiments - OT: FiOS auxiliary power for BBU

Keith Lofstrom keithl at kl-ic.com
Fri Feb 19 17:43:48 UTC 2010


On Fri, Feb 19, 2010 at 10:01:25AM -0600, Fred James wrote:
> "but not with a 0V battery" - I don't know - from the documentation one 
> might expect the BBU to shutdown leaving some "reserve" power in the battery
> Now, Verizon "tech" did say the aux port wasn't hooked up, but APC 
> couldn't understand that statement - i.e.: APC's documents contradict 
> Verizon's statement - but I don't know how to verify that either way?

Verizon is not in the business of telling the truth.  They are in the
business of keeping their equipment safe from hardware hackers like us.
Obviously, there are risks, starting with some clown hooking a car
battery backwards into that port.  If I was programming an Indian call
center, I would have them say whatever was necessary to keep people like
us from fooling with the customer equipment.  I'm grateful that they 
were willing to help me plug into the ethernet port on the ONT, rather
than route through the Actiontec cable modem as originally installed
(another story).  They could have told me to jump in a lake.

The aux port does hook up to the aux indicator light, and there is a
12.5V threshold, so it is not just a matter of an otherwise-unconnected
LED and resistor.  I imagine that under the right circumstances, the 
port will provide power though the BBU.

I'm guessing that replacing the good battery with an almost-but-not-quite
discharged one will cause the main BBU to draw power from the aux port.
The BBU control circuitry that does the switching may be powered off the
main internal battery, drawing a trickle of current.

If the external APC unit has a charger, then that is good news, because
it means the main APC unit is not trying to charge it, and probably
does not care how big the external battery is.  Car batteries are much
cheaper per watt-hour than the small gel cells, and you can keep them
on a trickle charger.  In extremis, you could even power the unit from
the battery in a car, BUT DO NOT CONNECT IT WHEN THE CAR IS RUNNING,
the ignition spikes would likely kill the APC BBU.

Keith

-- 
Keith Lofstrom          keithl at keithl.com         Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs



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