New battery installed but battery light on modem is not lit.
Which Xfinity Gateway do you have - XB3, XB6, etc.
I found a thread that says the battery is only for phone service:
Hello @Marbler1, thanks for reaching out to our Forums! Yes like @RobertWy asked if you could please provide us with the model of the gateway you have, that would be great. I also help the link provided was helpful. We're here to help!
@Marbler1, we never heard back from you on here, so I will be locking this thread. Please be sure to send me a PM if you still need assistance with battery backup concern. Please create a new Public post for any new issues or concerns, we're here to help! Thanks and we appreciate you being the best part of Comcast.
To send a private message, please click my name "ComcastAmira" then select "Send a Message" on the right side.