Mike, Good question and I had the same one for a local radio station (KRYZ LPFM). They have a radio transmitter, PC, network gear and a raspberry pi to power if the grid goes down and it does as it is in California and in the Sierra's. This also had to stay up for at least 5 hours for emergency comms and not cost a crazy amount as it is a community station. What I went with was a solar charger with no solar cells and a couple of high quality LiFEPO4 batteries. Everything was off the shelf and the solar charger has an app and with a bit of wifi I can “see” the status of everything. We pull about 200 watts max and double that when charging the batteries after a power outage, the solar charger is about 90% efficient. We recently had a snow storm power went out and we were up on the air for 5 1/2 hours with no problems, even though the batteries are 6 years old! Of course the hardware we purchased is way out of date now but new ones offer the same options, we used PowMr:- https://powmr.com/collections/all-in-one-inverter-charger All in One Inverters powmr.com For batteries which seemed to be the critical high quality thing to focus on we used https://battlebornbatteries.com/ Reliable Lithium-Ion Batteries battlebornbatteries.com The net result is neat remote and supportable, both companies where super helpful.. The only thing to be super careful of when building was the size of the cables to the batteries as I had to purchase equipment to put of the cable clamps and make sure everything has the right (big) fuses. Hope that helps.. Pic below of the solution in the transmitter shed. Colin Constable 
On Apr 6, 2025, at 13:49, Brandon Butterworth via NANOG <nanog@lists.nanog.org> wrote:
On 06/04/2025 19:55:20, "Mike Hammett via NANOG" <nanog@lists.nanog.org> wrote:
Most normal UPSes get terribly inefficient at lower load ratings.
You don't say how long you want to run for. Assuming the mention of extendable batteries means you are looking for several hours or more we've not found any small ones. Generally extendable batteries start with 1kVA or greater units.
Due to the lack of suitable devices some UK providers have resorted to -
https://www.ispreview.co.uk/index.php/2025/03/broadband-isps-vodafone-bt-kco...
but it relies on feeding the devices DC.
Our FWA sites are around 50W and are in cabinets so large batteries and feeding things DC is easy. We tend to power everything with POE so all that is needed is a switch with DC in (we've used Netonix but there are others such as Mikrotik).
For sites where we want a packaged system delivering AC we've used lightly loaded Eaton 5PX range with extra batteries and just accepted the efficiency, which has not been terrible.
There are plenty of consumer portable battery units that offer a lot more battery capacity than UPS generally have. Some operate as UPS and provide AC or DC out. If you feed your devices DC then there is no inverter low load inefficiency.
For example you could run all day on just a battery expansion pack (there are larger ones) https://bluettipower.co.uk/products/b80-expansion-battery which can be charged off an AC adaptor and not need the main unit.
brandon
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