For those who might wander into this thread via search, here are the distilled facts about the power supply, battery backup behavior, etc, of the BBU and ONT:
- The ONT itself is powered by 12V DC, which is delivered either via the BBU, which transforms power from an adapter (that adapter itself is transforming 110V to 48V/48 Watts for delivery to the BBU), or a "standalone" adapter which transforms 110V AC household voltage to 12V DC direct to the ONT. There is a poster in this thread who claims that the ONT accepts mains 110V AC, and that is incorrect.
- It is correct that, when mains power is down and the battery is the active power source, the only connection that is maintained is landline telephone service. The MoCA/Ethernet and Video services remain active for <10 minutes once the mains power is disconnected, at which point the ONT disables them, based on a signal from the BBU which tells the ONT that it is on battery backup power. (BTW, this behavior can be hacked, and internet/video can be made to remain connected even when on battery power. Google is your friend)
- If you currently have a BBU and an ONT, and the BBU is connected to the ONT with either a multi-conductor cable or a collection of ~7 loose wires connected between the BBU and ONT with terminal block connectors, you cannot simply delete the BBU from your setup. In addition to acting as a power adapter/battery charger, the BBU is giving the ONT additional information on the power status - namely whether the system is currently running on mains power or battery power - and the ONT behaves differently based on that information (see above bullet point)
- If you have the misfortune of having the 48V-12V transformer in your BBU die late on a Sunday evening, and you work from home (needing to ensure that the internet is going to be working first thing in the morning), you can do the following: (1) Make sure the BBU is unplugged, and the battery is also unplugged from the BBU (2) Swap the blue and gray wires between the BBU and the ONT. If you have loose wires connected to terminal blocks at either end, this is easy. If you have a bundled, multi-conductor cable between BBU and ONT, it does take a bit more work to open up the outer cable sheath, cut the blue and gray wires, and switch/solder/insulate them. It's not much more work though. (3) When you've finished your wire modification between BBU and ONT, plug the battery back into the BBU. This will turn the BBU on, and it will keep internet and video services powered. NOTE - the standard BBU battery is not going to keep everything up and running for more than a day. If you want a more semi-permanent fix until you can get a service tech out to your place to replace the BBU, you can hunt down a 12V ~1A wall wart power adapter, cut the barrel plug off, connect the +/- leads to the corresponding leads on the battery-to-BBU adapter, and plug the battery-to-BBU adapter back into the BBU (sans the battery, of course). When combined with the above-mentioned blue/gray wire swap modification, this fix will keep you up and running with all services, indefinitely.
