Suspect its a model built specially for BT.

https://amzn.to/3dUhUOM at £43.49 from same people would provide an hour of uptime with a load of around 20W, i.e. router plus ONT

I'd normally look at APC simply because used to their big data centre kit, but even on cheaper end I would look at ones where the battery can be replaced and is a fairly standard size.

Today we had the CBT's fitted on the tops of the poles, our CBT on the pole near me the fibre goes overhead to the next pole down the pole to the strain relief device then to the manhole at the bottom of the pole, it will then go about another 50M to a splice point and then a local node that is about 50M away near the main fibre runs along our main road.
They also put in a total of 4x Fibre cables in (3x 36fibre's and 1x 8 fibre's) into the ducts that go further down our village lane.

So it looks like my fibre connection will go from the CBT down the pole into the manhole (that was put in for me some years ago as I am the only house with an underground duct to our house in our lane ) then it will go from the manhole to our house underground into our porch, No CSP straight into the ONT.

The problem with any mains UPS solution is that they are inefficient on two accounts - there are losses in converting battery -> mains-like power -> original PSU back to DC, and for small loads the power consumed by the UPS becomes significant.

For the batteries used in small APC UPS (7Ah or 12Ah), an equivalent DC UPS solution will typically provide between 2.5 and 3 times the runtime. When building FTTP-based systems requiring backup I've done away with the Openreach supplied mains PSU, and BBU when they were being fitted, running the ONT directly off a float-charged 12v lead-acid battery.

It depends. The original CBT installations were connectorised cable from the CBT, strip outer sheath where the cable entered the premises, add a field-fit plug to connect to ONT.

AFAIK there have been issues with higher than expected failure rates of the field-fit plug so two connectorised cables are used - an outdoor one as before, but run to a CSP, plus an indoor one run from the ONT to a new-style CSP where the two are connected together. I expect this makes replacing the indoor or outdoor section due to damage easier as the entire CBT - ONT run doesn't have to be replaced. I'm sure the usual Openreach people can correct/elaborate...

That is what i was expecting, regardless of it being overhead or UG.

Ubiquiti do a line on this there is a 24V and 54V version, link to the 24V version below.

https://www.ui.com/accessories/edgepower-24v/

Can be used to power a number of their routers directly. Oh if only the ONT's could be powered with PoE....

+1

Today had another surprise when the contractors came back to my manhole opposite our farm gates and said they have to put in a 4 port CBT in the manhole just for my use with only one port being lit for my connection they ran the fibre from that all the way underground to where the slitter is going in the next lane.

I was trying to find out when it's going to be lit up, they said it's up to BTOR , that could mean weeks,months or years

Love that you have your own CBT.. but yeah I feel you pain ..

There are a number of companies (e.g. Mikrotik, Ubiquiti, Netonix, Tycon Power, PoE Texas) which produce a variety of so-called passive PoE products - mostly for outdoor APs and fixed-wireless access networks operating at nominal 24v (most common), 48v or 54v, but I've not seen much for nominal 12v.

Even though it isn't built in to the ONT you could potentially use passive PoE injectors to combine the DC + data over a single network cable if providing mains close to the ONT is problematic. Being 12v does limit the distance, you would drop around 0.5v on a 10m Cat5e cable for a HG8110 ONT which is fine. For longer runs you could use an active 802.3af splitter at the ONT e.g. https://shop.poetexas.com/products/gaf-12v12w fed from a regular PoE switch or midspan injector.