said by IowaCowboy:
YourBroadbandStore[dot]com (which is hosted by Arris) sells the batteries directly to consumers.
I am thinking of buying the 16 hour battery for my Arris TM722 (that I own) since I have a burglar alarm that uses the CDV line. The alarm has a battery that depletes after 24 hours before the system shuts down.
If Time Warner would give my grandma an Arris EMTA for her digital phone, then I could get a battery for her modem from Arris since TWC does not issue them. 16 hours is the longest battery that Arris sells for the TM722G.
solution would be for you to upgrade your grandma to 30/5 and they should be giving out ARRIS 852G or 862G modems in her area now that they have all in one DOCSIS 3.0 gateways available including EMTA and the only brand they are using for DOCSIS 3.0 EMTAs are the ARRIS ones.