I experienced the same exact thing - received a dual band modem without a backup battery when I exchanged a single band modem which had a backup battery, just as any other modem I had ever rented from Comcast until now. I noticed it within minutes of the installation and called Comcast to provide a "fully functional device as the previous modem was" and was told I had to purchase the battery for $35 dollars and $15 for shipping. At no point did anyone in the process of this exchange mentioned or pointed out that the new modem would not have a backup battery. Thus, I refused to pay Comcast for something they consider "optional part" but which I consider "essential in the event of a power outage" for 1) a device rented from Comcast, and 2) for telephone services that Comcast gets paid for... The several Comcast folks I talked to since this issue occured on Wed evening were unwilling to provide the battery. The backup battery is not needed for "normal operations" but it is needed in the event of a power outage for a service that can be life saving. As a result, I am now in the process of moving all my "comcast related services" off of Comcast to other providers. If this is the way Comcast believe they can treat a customer of 17 years, I am beyond dissappointed at their perception/stance.
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