You wont have a battery. In the UK they stopped providing a battery backup when they switched to the newer ONT quite a while ago, and routers typically do not include one either.

There are a few generic router battery backup products on the market but none specifically get advertised as working on the ONT, but many do. Realistically though they're utterly pointless when you can pick up a vastly superior APC UPS for the same price.

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bdavbdav a day ago | parent [-]

My plan is to stick my UniFi gateway / switch on a UPS, and get one of those power over Ethernet injectors / barrel jack extractors(?) to power the OR ONT.

Chatting to the BT guy that last visited, they reckoned the street cab would only last for half a day or so without power.

	▲	esskay 12 hours ago \| parent [-]
		Yeah for mine I've got the unifi cloud fibre gateway but currently use its sole poe port for a u7 lite. Thats on an APC UPS which will give me 3-4hrs life. Then for the ONT I've just picked up a relatively cheap Eaton UPS that should give it approximately 3-5hrs. TBH any outage longer than that and I'm out of the house for the day until its fixed!