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

[Keith Lofstrom]

I fiddled a bit with the "Auxilliary Power Supply DC 12V" input to
my FIOS BBU.

The barrel connector seems to be a 0.15 inch barrel (approximately
6mm), center positive.  I clipped the connector and cable off an
obsolete wall wart, and proceeded.  This is the same power connector
as some of the older Nokia cell phones, IIRC.

I set up a lab bench power supply with current and voltage limits,
and connected it to the cable.  When I increased the voltage above
12.5V , the "Auxilliary Power Source" light on the front panel lit
up.  The BBU drew less than 10mA.  I dialed it up to 13.5V, about
what a car battery puts out, and set the current limit to 5 amps.
Since the unit draws 20W from the line in normal operation, I 
assumed that would be enough.

I pulled the line power input to the BBU, the unit went on battery
as intended.  I pulled the internal battery connection, hoping it
would use the auxiliary power instead of the internal battery,
and the BBU shut down, without drawing current from the auxiliary
jack and bench supply.  It might have been a startup surge, so I
tried again with 0.086 farads across the supply.  Again, shut
down, no current from the bench supply.  I don't want to try a car
battery directly, too much current if something shorts.

So - a mystery.  Perhaps there is some protocol on the wire to the
approved external device.  For extended life, use an external UPS
on the line input, I guess.

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