Hopefully this pointer will help someone facing the same challenge - a couple of years ago, I realized that I wanted a battery backup for the ONT terminating fiber service to my house. I had about half an hour runtime for the entire equipment rack (~500W) but wanted to take it further and it made no sense to keep the internal network up without the internet connection. I looked at options for structured cabinets, like the Tripp Lite AV550SC, but none of them would fit in the existing large, but shallow, breaker cabinet.
By chance, I stumbled over a slim profile UPS designed for digital signage - the Xtreme Power Conversion J60: J60 Lithium UPS | Xtreme Power Conversion
It checked all the boxes in terms of fitment, safety certifications, warranty, and was lithium ion to boot. After adding standoffs to the mounting bracket and a low-profile supply cable, I was happy. The only downside is price - the 350VA version that I have costs around $320; the new 600VA around $640. At any rate, it has survived multiple power outages and it should power the ONT for at least one hour - preferably closer to the 2.5 hours I have available for the equipment rack.
By chance, I stumbled over a slim profile UPS designed for digital signage - the Xtreme Power Conversion J60: J60 Lithium UPS | Xtreme Power Conversion
It checked all the boxes in terms of fitment, safety certifications, warranty, and was lithium ion to boot. After adding standoffs to the mounting bracket and a low-profile supply cable, I was happy. The only downside is price - the 350VA version that I have costs around $320; the new 600VA around $640. At any rate, it has survived multiple power outages and it should power the ONT for at least one hour - preferably closer to the 2.5 hours I have available for the equipment rack.
