how old is the device’s battery? 

It was released in 2017 so the battery itself might be bad and need replacing (not sure if I’d invest any $ in that old modem/router). 

thanks for the response, it’s less than 2 years old; I noticed the battery light was not on previously, maybe the connection was not tight, it’s on now; I guess I’ll find out if it works during the next blackout;

what is the the newer model of this modem? I bought the SVG2482AC for the landline phone jack…..

pretty easy to test. Wait for the battery to charge and unplug it and see if it stays on. If it doesn’t, probably the battery. 

You might have only bought it 2 years ago but it was released in 2017. theoretically, it could have sat on a shelf that long somewhere and could be sketchy at best. 

I unplugged it and it failed. is the modem supposed to transparently cutover to battery power if the battery is good? Or is there some other reboot required? 

pulling the plug should simulate loosing power. It should switch over as far as I’m aware. I don’t have that device so can’t comment on that 100% but thats the goal of a battery backup

I contacted the vendor, it’s not refundable. They’re original batteries, as you say, perhaps from 2017, I bought mine early 2023.  It was probably a dud when I bought it. I didn’t think to check it at the time. Lesson learned. 

You can replace them. But not sure if I'd invest in a router that old

thanks for the responses. what router would you recommend? I need telephone, hi-speed capable, xfinity compatible, with battery backup, thanks, 

Battery backup makes it hard. What I'd do? Pickup a UPS (backup power supply). Use it with the current one and when you need to upgrade, because if the UPS, you have more options because you just need a router that does telephone

good idea, I’ll check  it out, thanks for your help.

Nice thing is that since its just a router/modem, it doesn’t take much power from a backup power supply. I’ve got a APC brand 425VA that backs up my modem/router/switches and have been rock solid. 

Thank you.  I’m not familiar with UPS other than surge protection.  How long can I expect the APC 425V to provide power to the SVG2482AC in a black out event? 

Easily over 30 minutes if its just the modem/router