Eaton 3S 550 BS

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.

A great looking and compact UPS and easy to mount. I've used the mounting holes that's meant for walls and reinforced it with a couple of heavy duty straps under my height adjustable table, because I didn't want a number of un-sightly cables risk getting caught as I raise my desk. On one side of the strip is surge protection and the other uses the UPS, I didn't know this at first as I skipped the instructions and was wondering why it wasn't working! I got this was for my NVMe RAID which is very sensitive when power is suddenly cut and I risk a 2 day rebuild/re-install, I've already had it come on twice when the lights started flickering and thank goodness I had this. It comes with a long USB cable for communication and my Mac already has a fantastic built-in feature that brings-up a message in the middle of the screen, warning you're now running on UPS battery and to save/back-up etc. there's also a battery level indicator on the desktop strip. I'm running a power-hungry 40inch curved LG monitor, a RAID SSD and NVMe RAID, Macbook M1 Max, various SSD HD, a Thunder Bolt 4 hub and a Wifi6e router - when the power goes, there is a low level alarm and I get around 7 minutes to save and power down, which is more than enough, but luckily we only get very short power outage in London. Highly recommended and everyone should get one to protect their IT equipment.

I own three of these units. Two worked great during a power cut yesterday, but one of them instantly dropped the output power. They are all around 12 months old. The one unit which failed had actually been fully discharged once, several months ago during a previous power cut. The other two units did not fully discharge, because they have very light loads (~3 watts vs the ~9 watts attached to the failed unit). Both of the lipo cells inside (TP LI-ION 3.7V ICR18650 2200mAh MH46259 UD020) now read at roughly 0.125 volts, so my /assumption/ is that these are unprotected cells and the unit itself does not have a low-voltage automatic cutoff. This is extremely problematic, because whenever there's a lengthy power cut, there is a solid risk that the unit itself will then be bricked unless you want to manually replace the lipo cells inside. So I'm afraid I need to give the "overall rating" as just one star because of this. Sorry, Eaton. Unless I'm mistaken and the one unit is faulty, then you will need to release a revision 2.0 which includes proper cell protection. Ideally they would auto power-off at, say, 20% power remaining. Perhaps even make the percentage/voltage configurable with a DIP switch somewhere, but obviously a DIP switch would add slightly to the materials cost & the plastics would need redesigning, so a straightforward X% cut-off would be the most reasonable thing to implement.

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 [email protected] 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 functions To 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 second chance ones have a high probability of damaged battery cells. I had to replace those,which is possible when you take it apart. But consider that it has no, again no, protection for deep discharging of the battwry cells inside. (2 x 18650)