Being that type of guy, a red LED glowing in the far corner of the basement attracts my attention:
Back in the day, Verizon didn’t make it obvious that the customer is responsible for replacing the battery keeping the ONT alive during power failures. I expect VZ would eventually let me know the battery was dead, remind me I was on the hook for the replacement, then offer to send a tech around with a Genuine VZ Battery to maintain reliable service.
It’s an ordinary 12 V 8 A·hr sealed lead acid battery and, yes, it’s been in there for a while:
However, being that type of guy, I just happen to have a box of not-dead-yet SLA batteries waiting for recycling:
They’re three years younger than the VZ battery …