Backup battery for voice/phone
I have an Xfinity supplied Cisco DPC 3941T, Wireless Gateway, XB3, modem/router combo. I want to buy a backup battery so when the power goes out I can still make phone calls with my old telephone (does not require a power plug/no base, just plug it into the wall port). I searched online and found a Pegatron brand, 3000 mAH which is made for this Cisco for $17.00, says it will power the phone for 8 hours (or maybe 8 hours worth of talk-time?). Per an Xfinity Chat, the rep said Xfinity would send me a battery for "about $100.00". Question: is the Xfinity battery THAT much better?