[Coco] Off-topic question for electronics wizards

[Christopher Barnett Fox]

Hey folks,

Sorry to send out an off-topic message, but it does relate to electronics,
so perhaps not entirely off the mark. I have a pretty basic question that
could probably be answered very quickly by someone with enough background,
and this list seems to have ample supply. I confess while I'm very
interested and willing to learn, I'm an electronics amateur.

My Verizon FiOS ONT backup battery, a GS Portalac PX12072 SLA, needs to be
replaced. This is a 12V 7.2Ah battery, used only to maintain voice
services in the event of a power outage. I do not have Verizon land-line
service (or any land-line service, for that matter), and only use
Verizon's FiOS broadband internet. The BBU doesn't provide any backup
supply for data services.

So, I don't want to spend the ~$20 to replace the battery, but the darn
ONT won't stop complaining about the missing/presumed dead battery, with
an obnoxious BEEP every five minutes or so.

Here's my line of thinking... could I "trick" the ONT's battery backup
unit into *thinking* it has a fully-charged battery by just using a 120V
AC to 12V DC transformer? I have loads of spare "wall wart" supplies
around, and I'm sure I could scrounge one up that provides 12V DC. Does
the output amperage matter?

Thanks for your time and expertise!

Christopher