Author Topic: [RANT] Why are domestic Uninterruptible Power Supplies such utter crap?  (Read 7525 times)

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Offline nfmaxTopic starter

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I'm trying to find a UPS to keep my network equipment running during power outages - 50W to 100W total load. I have an APC BackUPS 700 which I use for the PC. It's my second. The first had such dodgy output connectors that a careless touch against the output cable caused a power interruption to the load. The second was better at first, but is now developing the same problem. Further, I see they have changed the design to use a non-standard USB cable connector, for which they do not include a cable. And they are out of stock (permanently). And the thing takes enough power just sitting there doing nothing to keep it uncomfortably hot - about 15W.

I tried a CyberPower 'brick' type off Amazon. At least this one had a more respectable idling power consumption of 2 to 3W, once the battery was charged. I tested it using a 60W bulb load, which it managed to keep going for nearly 50 minutes, but the peak to peak output voltage was uncomfortably high to start with - 724V. That's equivalent to 256V RMS, more than the legal maximum here of 253V. It also got pretty hot while running. The killer feature was that it kept on getting even hotter while it recharged the battery, eventually setting off my smoke detector at 1am! Not actual smoke, just hot plastic.

That went back for a refund. Maybe it was a faulty unit, maybe a nasty cheap Chinese design.

Then I tried a local specialist supplier, and they recommended me a Riello NetPower NPW800. This one also takes 15W or so idling and gets uncomfortably hot while operating. Its real killer feature is that after 12 minutes or so of battery operation, a (tap-changing?) relay clicks, and the peak to peak output voltage goes up to 792V, equivalent to 280V RMS, and stays above the equivalent of 253V RMS for no less than 20 minutes!! I thought these things were supposed to protect against mains over-voltages, not generate them!

I used to have a trusty old Liebert doing the same job, but that finally died after 20 years service (several battery replacements, of course). We seem to be stuck with nasty knock-off copies of this same 30 year old design, cost engineered down to the point where they basically don't work. It's either that or spend thousands on a server rack grade UPS system, grossly over-specced for the job, and wasting even more power.
« Last Edit: May 21, 2021, 07:54:35 pm by nfmax »
 

Online thm_w

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How often are you plugging and unplugging stuff from the APC? Can you open it up and bend the pins back a bit?
I'm guessing most of the 15W is float charging of the lead acid battery, although they say 7W charging.

For the USB cable, if you have a RJ45 crimper you can make one yourself. About the same price to buy a crimper kit than buying that cable (~$25), many places selling the cable though.

It is crazy though that these type of devices can get away with not specifying idle current at all in their datasheet. Let alone meeting some sort of minimum standby power requirements.
Same deal with some power bars, etc.

Replacing the lead acid with LIFEPO4 would not be cheap but would end up in a superior UPS.
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Offline nfmaxTopic starter

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How often are you plugging and unplugging stuff from the APC? Can you open it up and bend the pins back a bit?

I never unplug anything from the APC, just accidentally touching the power cables when plugging RJ45's into the switch sat next to it.
 

Offline DrG

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I have used a CyberPower CP1200AVR https://www.cyberpowersystems.com/product/ups/avr/cp1200avr/ for the last eight years and have never unplugged it from the mains. Less than US$150. I have a desktop and a monitor plugged into it at all times. It has never caused me problems and has saved my butt many times. It has been particularly good at brief outages (flickers) I always hear the click on and computing goes on without any interruption - other devices that are not on the UPS do not fare as well and reboot/reset. When there is an longer term outage and I am here, I complete what I am doing and save the work and shut down. I don't know how long it would last, but it definitely makes it for long enough to do what I need to do.

Not sure if that helps, but I am happy with this one and, frankly, did not think it would last this long. If it fails tonight, I will buy another one tomorrow.
« Last Edit: May 22, 2021, 01:49:42 am by DrG »
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Offline redg

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Replacing the lead acid with LIFEPO4 would not be cheap but would end up in a superior UPS.

There are several threads about doing this on Will Prowse's DIY Solar Forum: https://diysolarforum.com

The forum covers LiFePO4 batteries independently of solar, and the threads come up with a search for UPS in the title.

It is more expensive and more complicated than using AGM batteries, but there's a decent argument that it makes financial sense over time. If you can anticipate outages, or "uninterrupted" isn't important, something like a Jackery may be the way to go, especially if you have other uses for portable power.

I recently set up a LiFeMgPO4 battery (Lithium Werks Valence, photo below) and 300W (600W peak) inverter. It's an excellent, reasonably light portable power source, but I haven't tried to make it work as a UPS.


« Last Edit: May 22, 2021, 11:34:10 am by redg »
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Offline james_s

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While I won't say the consumer UPS units are amazing quality, I still have not had the problems you're having. I have about half a dozen UPS units in my house, a mix of APC and Tripp-Lite and they all do the job. I looked for ones that are Energy Star certified and the standby consumption once the battery is charged is only 2-3W. The Tripp-Lite units are particularly nice in that they use an inverter topology that doesn't rely on an iron transformer and at light load they are significantly more efficient than the APC units I have although the downside is that you have to unscrew and open the whole housing to replace the battery. I have never seen unusually high voltages out of any UPS, mine all tend to produce around 110-115V relative to the 120V nominal line. They are "modified sine wave" which is really just a square wave with dead time so the peak and RMS values match those of a sine wave.
 
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Offline ChuckDarwin

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@redg,
Cut off leads in the centre of the battery-dual lead system?
 

Offline redg

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@redg,
Cut off leads in the centre of the battery-dual lead system?

Those ports are for data cables used to connect these batteries in series, which I'm not planning on doing.

The battery is part of this series of batteries:



Will Prowse did a teardown about a year ago. I did not pay $1250 :) It was excess inventory, full capacity, and I paid just under $200.

« Last Edit: May 26, 2021, 09:52:20 am by redg »
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Offline nightfire

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In short: you get what you pay for. Those small units that can be sold for 100-200 $$$ or €€€ usually consist of a small voltage input detector and some switching relay to keep costs down.

If you want real quality, that also is able to filter out the usual garbage from the net input, you have to go double-conversion or at least some high-quality line-interactive UPS with netfilters...
And those are way more expensive, but the overall quality is a different league.

At work in our small server room I have 4 2kVA units as an a/b system setup, and including remote management cards I am quite happy with them- but those were around 1000 €/piece...
 

Offline todd_fuller

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I went down a similar path about a year ago. I went through a series of consumer UPSs over time. Moving up each time thinking they were going to perform better. 

 I ended up buying a Liebert GXT4 1500VA UPS. Double-conversion, hot-swap batteries, network management, load shedding, etc, etc. You can get them for less than $300 w/ fresh batteries. If you decide you need more runtime, many of these enterprise units have capability to add additional battery packs.

For anyone considering this path, carefully look at the kind of plug the unit needs. Pretty much >1500VA is going to have a plug most of us don't have in our homes (in US). Also, before you jump into the online or double-conversion models, consider the noise level of the fan since they run the inverter 100% of the time and it needs cooled. 

 

Offline james_s

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I don't think most people would want one of those in their home, I certainly wouldn't, simply because of the poor efficiency. I'd be surprised if they manage better than 80% on a good day, which means you're throwing away a significant percentage of the power flowing through it as heat. I tested a bunch of different UPS's I scrounged and rejected anything that consumed more than 3W idle with the battery charged. It adds up over time, especially when you have several of them spread out in different places.
 

Offline bob91343

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APC has always been on my don't buy list.  Their advertising is worse than objectionable, or at least used to be.

Tripplite is famous (with me) for marginal design.  Very cheaply made.

So what does that leave?  I would lean toward DIY if you have the time, patience, and competence.
 

Offline james_s

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All of the 6 or so UPS units I have in service currently are either APC or Tripp Lite, they've all worked flawlessly, a few of them are more than 10 years old. I don't understand what the issue is? I've been inside them and they're built like any other consumer electronics, not spectacular but perfectly adequate. I had a couple of Eaton units that were nice too but I gave them away because their standby draw was almost 5W, around double that of the APCs.
 

Offline nfmaxTopic starter

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All of the 6 or so UPS units I have in service currently are either APC or Tripp Lite, they've all worked flawlessly, a few of them are more than 10 years old. I don't understand what the issue is? I've been inside them and they're built like any other consumer electronics, not spectacular but perfectly adequate. I had a couple of Eaton units that were nice too but I gave them away because their standby draw was almost 5W, around double that of the APCs.
The one UPS I have tried with a standby consumption less than 15W proceeded to wake me up in the middle of the night by setting off the smoke detector. The second unit applies an excessively high peak-to-peak voltage* to the units it is supposed to be 'protecting', and takes about 18W idling with a fully charged battery.

(*) The RMS voltage is within specification, but we are all EE's here, aren't we?
 

Offline SeanB

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Try to find a tossed out rack mount UPS, which will very likely just need new batteries, but is tossed out because the typical rack user will only buy OEM, which works out at being around the price of a new one. Got 2 of them for free from a local IT company, just ask them if they have some around, you will get typically IEC connectors on the input and output, though some have high current versions, so you will need to buy the rewireable cable sockets to use them. Using an APC 750XL at the moment, with the batteries external to it, as the ones it came with were stone dead, and I wanted more run time, so 2 60Ah car batteries are now plugged into the external battery socket.

The 2 rack mount units, one Eaton and one APC, probably work perfectly, just that I have never put new batteries in them, as they need 36 or 48V to operate, and I did not have the spare SLA batteries around to test them, the internal cells were well cooked. Heavy units, even without the batteries, so would probably work well and give you more than you need.

With your networking equipment it likely will run fine off 12VDC, so a simple UPS would be to have a regulated battery charger and a 12V battery, and connect the equipment to this instead. Easiest way to do this is to look for a security system power supply, which has a power supply that charges a SLA cell, and also provides operating current for the cameras and DVR from the battery. Lowest losses, though the charger/power supply will lose around 5w in operation providing the regular load.
 

Offline james_s

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The one UPS I have tried with a standby consumption less than 15W proceeded to wake me up in the middle of the night by setting off the smoke detector. The second unit applies an excessively high peak-to-peak voltage* to the units it is supposed to be 'protecting', and takes about 18W idling with a fully charged battery.

(*) The RMS voltage is within specification, but we are all EE's here, aren't we?

Well none of mine have that problem. They don't run hot at all, and how could they when drawing only 2.5W? None of mine produce an excessively high peak to peak voltage either, I've looked at them all on a scope, and all of mine produce a square wave with dead time so the peak to peak voltage is lower than that which comes out of the wall. The RMS is a tad low on mine too, 110-115V rather than 120V but it's adequate for keeping the equipment powered. I just have not seen any of these issues that people are complaining about here, it sounds like a defective device or a particular model that has issues, not an entire brand or class of devices. At the last place I worked where we had desktop PCs we had dozens of APC UPS's and I don't recall ever having any problems with any of those except for faulty batteries when they got older.
 

Offline nfmaxTopic starter

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I have emailed details of my test measurements to the local supplier, and they phoned me back. They are escalating the case to Riello - it may be a faulty unit. It still takes too much power when in idle mode, though that could be part of the fault too.

Look at the waveform - the 'on' time each cycle is much too narrow.
 

Offline oPossum

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Vrms of 235 indicates that the pulse width is close to what is should be for a "modified sine" inverter.
 

Offline nfmaxTopic starter

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Vrms of 235 indicates that the pulse width is close to what is should be for a "modified sine" inverter.

Nooo!! For a 20ms cycle, the ON time in each direction must be about 7ms for the crest factor to come out correct, so that both the RMS and the peak voltages are the same as a sinewave. Otherwise you could equally well apply a 200 microsecond pulse of 11kV in each direction, which gives a perfectly reasonable 220VRMS
 

Offline oPossum

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Peak voltage is only about 15% high. Put a load on it and you will probably see the peak voltage go down and the pulse width increase.
 

Offline Tom45

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The various Cyberpower units that I use have always been trouble free over the years.

I wonder if the 240 volt units are more prone to trouble due to marginal design at the higher voltages compared to the 120 volt units that we use in North America.
 

Online David Hess

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I used to have a trusty old Liebert doing the same job, but that finally died after 20 years service (several battery replacements, of course).

My last three UPSes have been refurbished Lieberts.  They all still work.
 

Offline james_s

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I just did a quick check during my lunch break. This is a Tripp-Lite Internet750U which I've had in service for about 2 years. It's certainly not something I'd use to power life support equipment and like any other UPS that uses those poor little tag terminal SLA batteries I would not load it up to anywhere near the claimed 750VA rating but for what I've asked of it, it has reliably delivered. Looking at the RMS and pk/pk values they look pretty reasonable to me. It's possible that most of these things are designed for 120V and then tweaked a bit to make them kinda sorta work ok in 240V land, I really don't know. As with most things in life, YMMV but I would not hesitate to recommend one of these to somebody with a similar use case as my own, which is keeping about 60W of IT gear running long enough for me to finish what I'm doing and then get out my generator and set it up at a leisurely pace.
 

Offline NiHaoMike

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With your networking equipment it likely will run fine off 12VDC, so a simple UPS would be to have a regulated battery charger and a 12V battery, and connect the equipment to this instead. Easiest way to do this is to look for a security system power supply, which has a power supply that charges a SLA cell, and also provides operating current for the cameras and DVR from the battery. Lowest losses, though the charger/power supply will lose around 5w in operation providing the regular load.
Use 3S 18650 packs, cheaper than sealed lead acid (especially for small packs) and matches more or less perfectly with 12V - about 4V/cell.
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Offline redg

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Use 3S 18650 packs, cheaper than sealed lead acid (especially for small packs) and matches more or less perfectly with 12V - about 4V/cell.

I don't think that lithium-ion or LiFePO4 cells are a simple drop-in replacement for lead acid. I would not use a lead acid charger with my lithium-ion and LiFeMgPO4 batteries, and I'd have reservations about maintaining them at 100% capacity indefinitely. I don't see how they are initially cheaper than lead acid unless you're buying used cells from, say, Battery Hookup, or ordering cells from China, which currently takes up to three months for delivery to the U.S., and involves substantial shipping charges that make it uneconomic for smaller capacity builds. For those options, you have to assemble the battery yourself, which has additional costs including buying a battery management system (LiFePO4 definitely needs one, and I suspect that the same is true for lithium-ion), an enclosure, bus bars, cable and connectors.

That said, there have been a number of discussions about using LiFePO4 for a UPS on Will Prowse's forum at https://diysolarforum.com. I do think that the battery discussed in posts #5 and #8 above would be cheaper than lead acid over time, assuming that concerns around setting it up as a UPS were addressed. I'd be more comfortable doing it if I had a couple of LiFePO4 batteries and a use, apart from a UPS, that involved draw/discharge. Then I could change out the batteries between the UPS and the use that drew down capacity.
« Last Edit: May 26, 2021, 11:17:44 am by redg »
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