home router battery backup

Jordan jnh at vt11.net
Mon Jan 17 22:26:07 UTC 2022

On Thu, Jan 13, 2022 at 10:29:13PM +0000, John Lightfoot wrote:
> In Vermont I have a Tesla Powerwall that Green Mountain Power
> paid for if I agreed to let them manage it.  Since then I've
> never had an outage of any kind, I usually figure out that there
> is one by seeing my neighbors' lights go off.

Wow, that's a nice program.  Do you know what they keep the
"reserve percentage" set to, the proportion of stored energy that
will never be discharged for grid-support, but held back for
island-mode use in case of an outage?

> I've also had great luck with my ISP, which is Comcast.  Even
> before we had the Powerwall, when the power would go out the
> (older) Comcast router would work on its own battery backup and
> my laptop would flip over to battery power, so I didn't have any
> loss of connectivity even then.

In my part of northeast Florida, although Comcast has installed
outside-plant batteries when extending service to new developments,
as of 2015 they would wait until customers complained (or perhaps
until "enough" ordered their voice service) to upgrade older

Service in my area used to drop immediately at even a fractional-
second grid power glitch, despite having many hours of backup on my
end.  It took about two months of nagging them to get the Alpha
Power box supporting our fiber<->coax node and line amps replaced
with one containing batteries, and nearly as long for a friend
across town in the same position.

Although I don't have Comcast voice service, instead using my own
over-the-top VoIP, several neighbors already did by this time.  I'm
surprised they weren't concerned for liabiilty over failed 911 calls.

Hopefully this policy has improved in the years since, but their
lack of proactive replacement of failed outside-plant batteries
suggests otherwise.  Rather than changing these out on a schedule,
or when failure is signaled by the equipment, they still appear to
wait until someone complains, after which expired batteries *might*
get swapped in a month or so.

Voice-capable gateways and eMTA's provided to Comcast Business
customers do contain lithium batteries good for several hours of
service, longer than most PBXes are backed up for, but of course
these are of no use when the outside plant lacks backup.

For residential customers, they seem to be charging a considerable
premium for the battery option:


"A backup battery for certain Comcast-provided modems can be
purchased from Comcast at any time and are currently priced at
$165, plus tax.  Your purchase includes 24 hours of standby time, a
one-year warranty and monitoring to determine when you need to
purchase a new battery."


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