Eaton3S 850B UPS - Off Line Uninterruptible Power Supply - 3S850B - 850VA (8 BS outlets, 2 USB Type-A ports, Quiet, Shutdown software) - USB interface (cable included) - Black&White

This review is based on initial impression, it's not a long term review!Very easy to setup and works great with Network UPS Tools + Home Assistant. I really appreciated the fact that it accepts standard UK power sockets, rather than the kettle leads inputs I've seen on other UPS's.The item is very heavy probably due to the batteries inside but the product itself feels very sturdy. I have my router and a few other bits of critical equipment plugged into it, and looking at the metrics my stuff mostly only uses about 100w, so in the event of a power cut I should get about 30-35 minutes of power, which is enough to shut things down cleanly.I tested a "power cut" by flipping the breaker in my consumer unit and the UPS kicked in instantly and kept everything going which gave me enough confidence that it's working. I've not had a power cut since installing the unit but I'm pretty confident it should work!

I bought this UPS a couple of months ago because the mains was becoming unstable with the lights flickering badly etc. (later traced by the utility company to a poor connection out in the street). Two days after I installed it and connected my PC, Router and Smart TV, the mains went unreliable with more flickering lights and clocks resetting etc., but the connected router and PC just continued working as normal. There have been a couple of momentary mains outages of a few seconds since and again the PC etc. had no problems.I also discovered on the Eaton website there's a form to fill in for the monitor software, I put something like private domestic user and was sent a link to a slightly older but perfectly functional and useful piece of software to monitor the current status and alarms.The distance between the two rows of sockets for filtered and filtered+UPS is larger than on some other UPS units which means some bulkier adaptor type plugs rather than the normal plug size can be accommodated. It also has a slide out panel on the base giving access to the battery which means it can easily be swapped out when at the end of its serviceable life. This makes me think this is a unit built to last.I am very pleased with my purchase which is performing flawlessly and wouldn't want to be without it.

Edit. 2 years later I’ve repeated some full discharge and recharge tests, including discharging it at the max rated 36Watts and unlike others still have has no problems with the recharge sequence. The failure of the low cell voltage protection reported by some hasn’t occurred on my unit. This Eaton3S and the APC CP12036Li remain the best options available for anyone looking for a small DC UPS with a recognised name.Nicely made mini UPS from a recognisable name, with a 2 year warranty its got the feel of a quality product. Well documented. It has some nice features, like switchable output voltage level and a relatively high supply rating of 36Watts. I've run some12V load tests when on battery and the output voltage only dropped from 11.9V@0.5A to 11.3V@3A. The DC output level was also maintained well as the battery ran low . By including the AC/DC conversion inside the unit there is only space to include 2 off 2200mAH lion cells, so overall capacity is a fairly small but usable 11.9Wh (measured). So it should be able to run a typical small router (5-6Watts) for around 2hours, that's probably long enough for most typical mains power interruptions.The battery recharge rate is a relatively low 4Watts so once mains power is restored it does take around 5Hours to fully recharge . Once fully charged the UPS appears to use <1W to manage its own functionsTo make it a better prospect than its competitor MiniDC UPS What it ideally needs is either larger internal batteries or perhaps the ability to recharge from an external powerbank. The case would benefit from some mounting holes and there's also no audio warning to indicate 240V power failure. It is however one of the few MiniDC UPS that I'd be content to leave running unattended in my house 24/7/365.

The battery backup had failed at some time, but even worse, after two mains power cuts in the early hours of one day, my 3S Mini UPS started randomly interrupting its output several times every day!The interruptions my router suffered were so short that they were noticeable only when I was streaming video, but the attached section of the chart supplied by my internet provider shows just how many there were each day, starting with those two mains cuts on 04 April.In future, I plan to simulate power cuts to my new better reviewed UPS every so often by simply cutting its mains power. So easy to do, what it is meant to handle, and definitely worth the effort.