Concept: battery backed up PC ATX power supply

[VinzC]

Hi all.

I do have a UPS for my computer and equipment. What I'd like is to combine UPS features with a traditional PC power supply, i.e. the main circuit would be designed like a car PC PSU to draw power from 12V batteries but for home, not automotive use. The PSU would be powered from the grid and only from the battery in case of mains outage.

I know this sounds like an uninterruptible power supply such as MGE's but the concept I'd like is different. A traditional UPS is an inverter that outputs mains voltage and uses the battery for backup. I find it silly to go from low to high voltage and then to low voltage again just because the PSU input is mains when everything works with 12V max...

What I'd like is to eliminate that inverter stage and use a single but high power 12VDC source to output the voltages required for a computer (+/-5V, +/-12, +3.3V), like a 300W PSU would. And to that the power supply would use the mains power to charge the battery when needed but would supply a unique, high-current 12V.

Do such power supply units exist? (I'm asking because I have found none so far.)

[Benta]

Do such power supply units exist?

No. They make no sense and would have duplicate a lot of the circuits in the existing ATX supply.

[VinzC]

Do such power supply units exist?

No. They make no sense and would have duplicate a lot of the circuits in the existing ATX supply.

I think you didn't get my point: the purpose is to *replace* the traditional PSU, no to plug to it so of course they make sense.

Search HDPlex.

Thanks for the link. However I see none that would embed a battery backup. Do you have an item as a reference?

[Siwastaja]

Now as li-ion has been cheaper, more robust, and better in every imaginable way for years already, it would be weird to design anything around the 12V lead-acid voltage anymore. 3s li-ion is close; but neither 12V LA or 3s li-ion matches the ATX spec anyway, so does it matter?

Looking at both simplicity and efficiency, I would like to eliminate all redundant power conversion steps. I bet most 12V PC stuff would work just fine with significantly larger voltage range, as the 12V is just a completely arbitrary voltage and is locally bucked down to several voltages, highest of which tends to be around 5V, and most power is consumed in lowest (around 1V) core supplies.

Of course it would violate the ATX spec, but it could be interesting to try tying a 3s li-ion pack to the "12V" line. The cells would float at 4.00V/cell, which is quite acceptable at around 80% state of charge. At about 20% state-of-charge, the pack would be around 10.3V, which shouldn't pose any actual problems, unless a specific device monitors the input voltage too eagerly, being "too smart" against out-of-spec ATX 12V. This would need to be tested.

Generating the required 5V/3V3 lines would be a walk in the park, as they tend to be low-power lines, and accepting one extra conversion step for them wouldn't be an issue. Most of the power would run with zero extra conversions compared to a non-UPS system.

For this to work, the standard ATX supply would be replaced with one that can support CC operation without faulting, for charging the battery after the outage, and small buck converters added for 5V,3V3 low power supplies. Apart from the battery itself, the cost and complexity is about the same to a bog standard non-UPS ATX supply.

This is basically how laptops internally work. I'm 100% positive something like this is used in some server hardware, as well.

[NiHaoMike]

I have done a few DIY designs of that type. Pretty much I just devise a way to get regulated 12V from either battery or mains and use DC/DC converters for the rest. Here's the first one I did, still working great after about 7 years of service:

[orion242]

Why not use a 12v ATX power supply and just keep the batteries topped off via mains.  Pretty sure 12v ATX power supplies are readily available.

[Red Squirrel]

What I'd like to see is PSUs that take 48v as input.  Then you just have a single large 48v battery bank on float with DC breaker panels and distribute power that way.  Just like telco gear.  They DO make them but they are very hard to find.

I've found when it comes to this stuff it's easier to just have an inverter setup and run everything at 120vac.  Like in my solar shed I did everything 120v.  It's just easier as 120vac stuff is readily available.  Switches, breakers, fixtures, pretty much any device imaginable etc. 

I had toyed with doing my server room all 48v but trying to actually find 48v stuff as a consumer is very hard.  You can't just order that stuff of Tigerdirect or Newegg etc and hardware stores won't have anything of that nature either such as breakers and so on.    So when I do upgrade my setup I will do 48v, but straight to a pair of inverters which will then power the PDUs. That way everything after that is going to be standard gear.  There is more power conversion involved though so it is a bit less efficient.

I eventually want to get into playing with lithium or LIFPO4 batteries too but they are harder to find and more expensive. You also have to filter through all the fakes.   So sticking to lead acid for now.  It is still king in these applications.   I think that will slowly change over time.

[NiHaoMike]

What I'd like to see is PSUs that take 48v as input.  Then you just have a single large 48v battery bank on float with DC breaker panels and distribute power that way.  Just like telco gear.  They DO make them but they are very hard to find.

I've found when it comes to this stuff it's easier to just have an inverter setup and run everything at 120vac.  Like in my solar shed I did everything 120v.  It's just easier as 120vac stuff is readily available.  Switches, breakers, fixtures, pretty much any device imaginable etc. 

I had toyed with doing my server room all 48v but trying to actually find 48v stuff as a consumer is very hard.  You can't just order that stuff of Tigerdirect or Newegg etc and hardware stores won't have anything of that nature either such as breakers and so on.    So when I do upgrade my setup I will do 48v, but straight to a pair of inverters which will then power the PDUs. That way everything after that is going to be standard gear.  There is more power conversion involved though so it is a bit less efficient.

I eventually want to get into playing with lithium or LIFPO4 batteries too but they are harder to find and more expensive. You also have to filter through all the fakes.   So sticking to lead acid for now.  It is still king in these applications.   I think that will slowly change over time.

You could do HVDC at 170V or 340V, which works with standard PSUs and is also trivial to derive from mains with a simple rectifier. DC rated breakers and switches are a little hard to come by but easier than before thanks to the popularity of solar power. Trapezoidal wave AC and pulsed DC are also worth looking at.

[mariush]

Problem with low voltage is the current and high losses due to wire resistance
You have a pc peaking at 3-400 watts... that's 30+ A ... you'd need a bunch of thick wires between psu an pc.

There's also issue of power stages / mosfets being optimized for ~12v ... with 48v in, you'd have a hard time designing cpu and gpu vrms

I'm of the opinion that standardizing around  20v +/- 5-10% would make sense... 20v is usb standard voltage, we already have laptops using 16.5v .. 19v adapters so mosfets and ICs exist to run directly with 20v , 18v..22v means low volume cheap easy to make polymer capacitors can be used and not least it's considered a "low voltage"... and good compromise (can make  itx systems that use <65-90w powered from 19v barrel jack or usb 20v or thunderbolt for example power pc from monitor's psu or could have  1000w psu with loads of 4pin awg16 20v connectors (each good for 10-15A or ~300w each)
 
So a new revision of atx psus could add 20v , make 12v less important (fans - but 24v fans can work just fine with 20v so could just relabel as 20v or re-engineer for 20v, mechanical drives, rgb crap, backwards compatibility with video cards) and 5v could remain for usb and other things. Could make stand-by 12v or 20v as well, for higher efficiency. Drop 3.3v and -12v ... a dc-dc converter on mb can  produce 3.3v for m.2 and pcie slots, cleaner, in small area, and no need for 4+ pairs of 3.3v+gnd wires in 24 pin conn. for it.

Could have power supplies made with alternate dc in (24v) ... 2 lead acid batteries in series give you ~20v..26v... enough for dc-dc converter inside to produce clean 19..20v (20v +/- 10% would allow min 18v)

I think one could even add 20v to pci-e by adding an extension (like they did with agp pro), backwards compatible.

[rrinker]

 This is (and has been for a long time) been done in telcom, where +/- 48VDC was common. I remember getting a tour of a then new fiber node which had racks of 48V equipment and the power supplies included the batteries, they didn't take in 120VAC, and output 120VAC to yet another stepdown to 48VDC, they took in 120VAC and output +/- 48VDC.
 Several PC makers offer rack mount servers with a 48V power supply option.

 here have also been PC power supplies that incorporated the UPS. The 48V was a compromise, needed for the telcom ring circuits but also not so low as to need really heavy cable. You try to run no more than 12V DC in server racks and you will need some really thick cable to avoid voltage drop.
 

[wraper]

No. They make no sense and would have duplicate a lot of the circuits in the existing ATX supply.

I think you didn't get my point: the purpose is to *replace* the traditional PSU, no to plug to it so of course they make sense.

The thing is, it would be the same as connecting 2 separate PSUs in parallel unless you power it from 100+V of batteries. In such case it would be much easier to do.

[Red Squirrel]

What I'd like to see is PSUs that take 48v as input.  Then you just have a single large 48v battery bank on float with DC breaker panels and distribute power that way.  Just like telco gear.  They DO make them but they are very hard to find.

I've found when it comes to this stuff it's easier to just have an inverter setup and run everything at 120vac.  Like in my solar shed I did everything 120v.  It's just easier as 120vac stuff is readily available.  Switches, breakers, fixtures, pretty much any device imaginable etc. 

I had toyed with doing my server room all 48v but trying to actually find 48v stuff as a consumer is very hard.  You can't just order that stuff of Tigerdirect or Newegg etc and hardware stores won't have anything of that nature either such as breakers and so on.    So when I do upgrade my setup I will do 48v, but straight to a pair of inverters which will then power the PDUs. That way everything after that is going to be standard gear.  There is more power conversion involved though so it is a bit less efficient.

I eventually want to get into playing with lithium or LIFPO4 batteries too but they are harder to find and more expensive. You also have to filter through all the fakes.   So sticking to lead acid for now.  It is still king in these applications.   I think that will slowly change over time.

You could do HVDC at 170V or 340V, which works with standard PSUs and is also trivial to derive from mains with a simple rectifier. DC rated breakers and switches are a little hard to come by but easier than before thanks to the popularity of solar power. Trapezoidal wave AC and pulsed DC are also worth looking at.

Was thinking that too actually.  Need way more batteries/cells to form a string mind you, but it would be overall more efficient too.   May need to modify some PSUs just to make sure the hot/neutral pins are all matching positive/negative but other than that it should in theory work.  Could use standard power outlets and cords too I think.   Just not switches or breakers as arcing would be an issue.

[VinzC]

Well, first off thanks to all for your insights.

The idea comes from having seen car PC power supplies, like this one or that one. For having used one in a car PC, I know some do work. Of course the one I tested was powering just a motherboard alone without an external video card but you get the concept. Since there are also 12VDC power supplies (SMPS connected to mains) of various peak current, combining the two with a battery and charger should be possible, that's what I thought.

Note that I don't necessarily want to stick to 12V or 300W — I have to measure the peak power consumption of my equipment beforehand. Two batteries in series would do as well. I'd just like something that would avoid going to then from high voltage.

BTW, by the law of conservation of energy, upping to 220V (or 110V) should be no different than straight from the battery, right? The inverter draws the same amount of power from the battery even if it outputs mains voltage, right? So, yes, that'd imply using thick sections. For having worked in a company that makes its business from stretching luxury cars (which implies cutting and stretching power cables), I've seen some big stuff from the automotive industry .

The thing I don't know is how stable the 12V line must be and what its voltage swing it shall be for a PC motherboard.

Kudos to NiHaoMike for the pics. That looks messy but *very* interesting. Do you share the schematics?

EDIT: I also forgot... I'd also like to stay away from lead-acid batteries as the place I'm thinking of putting my power system is not well ventilated, i.e. no straight path to the outside walls.

[windsmurf]

See:
http://www.nipron.com/dc_ups/dc_ups/

[NiHaoMike]

Was thinking that too actually.  Need way more batteries/cells to form a string mind you, but it would be overall more efficient too.   May need to modify some PSUs just to make sure the hot/neutral pins are all matching positive/negative but other than that it should in theory work.  Could use standard power outlets and cords too I think.   Just not switches or breakers as arcing would be an issue.

Probably would make more sense to use DC/DC converters from lower voltage batteries unless you're dealing with very high power levels.

[VinzC]

See:
http://www.nipron.com/dc_ups/dc_ups/

So they exist!

[wraper]

See:
http://www.nipron.com/dc_ups/dc_ups/

So they exist!

And their efficiency spec is so piss poor that even running a good standard ATX PSU from half decent UPS or inverter will be more efficient. Not to say efficiency during normal operation.

[David Hess]

They used to make ATX power supplies like that.  They had a lower intermediate voltage which was the same as the backup battery's voltage so essentially they were a online UPS combined with a power supply.

The easiest way to do it now is probably to use one of those 12 volt input power supplies intended for low power systems with a battery and 12 volt power supply/charger.

[dzseki]

It depends on your power needs. There is a thing called "PICO PSU" which is a small DC/DC convcerter that plugs right in the ATX connector of your mobo. All it needs is a 12V input, the output power is limited though: 120-160W I think. But with that you are almost done.

[VinzC]

See:
http://www.nipron.com/dc_ups/dc_ups/

So they exist!

And their efficiency spec is so piss poor that even running a good standard ATX PSU from half decent UPS or inverter will be more efficient. Not to say efficiency during normal operation.

Let alon[e] their reliability is not that good. We have a Hesse Mechatronics wire bonder and its control computer runs a Nipron PSU. It failed at around 4 years into service (totally less than 4k hours of use).

Woah, guys, wait. It's only about someone here (whoever it is doesn't matter) claiming such PSU's don't exist and make no sense. Someone else (whoever it is doesn't matter) responded with a link to an actual reseller, making the point and that's it. The rest (about efficiency et al.) is something else. If there's one supplier for such power supply units, logically then there must be others. That's the point. All I have to do is find a good one.

There's still some good power supply to find given my equipment's consumption. There is also building one, just like NiHaoMike did if none fits. Such kinds of PSU's deserve to exist IMHO, there should be more.

[David Hess]

These looks similar to the ATX power supply which included battery backup that I remember:

https://www.sunpower-uk.com/product/atx-power-supply-with-ups-function-2/
https://www.trumpower.com/medical/mpc.html
http://www.nipron.com/dc_ups/dc_ups/

One of the interesting features of the one I remember was an innovative thyristor based inverter which allowed the ATX power supply to also supply AC backup power to the monitor.  This was almost pre-internet so good luck trying to find it.

[tooki]

Years ago, google stopped buying off the shelf motherboards and began having them custom built, and one of the modifications they did was to have direct 12V DC input plus a direct battery input on the boards instead of using AC PSUs and UPSes:
https://www.nytimes.com/2006/09/26/technology/26google.html

But it looks like more recently, they’ve begun moving to the 48V telecom standard rrinker mentioned: https://datacenterfrontier.com/google-unveils-48-volt-data-center-rack-joins-open-compute/

[jmelson]

What I'd like is to eliminate that inverter stage and use a single but high power 12VDC source to output the voltages required for a computer (+/-5V, +/-12, +3.3V), like a 300W PSU would. And to that the power supply would use the mains power to charge the battery when needed but would supply a unique, high-current 12V.

Pico PSU makes some power supplies for mini-ITX motherboards that run off 12 V DC and other voltages.  These are for lower-power machines, not the top of the line gaming monsters.  The entire PSU is a little PC board that plugs into the motherboard power connector, and has a few cables dangling for the hard drive and CD drive.

Jon

[Stray Electron]

Why not use a 12v ATX power supply and just keep the batteries topped off via mains.  Pretty sure 12v ATX power supplies are readily available.

   I was going to say the same thing.  I picked up a bunch of embedded computers that had 12VDC power supplies that look like these from E-bay https://www.ebay.com/itm/Pico-PSU-120-12V-120Watt-DC-DC-ATX-Power-Supply-for-Mini-ITX-Mainboard/333192561048?hash=item4d93d30198:g:Z3QAAOSwfz9c1y7e.  I can't say if the E-bay ones are any good but the ones that I have look identical and came from a very demanding commercial application and I haven't found a bad one yet.  These plug directly onto the ATX power connector, connect 12 VDC to the input and away you go. They also have a cable with connectors to power the  hard drive and floppy drives.

[windsmurf]

Why not use a 12v ATX power supply and just keep the batteries topped off via mains.  Pretty sure 12v ATX power supplies are readily available.

   I was going to say the same thing.  I picked up a bunch of embedded computers that had 12VDC power supplies that look like these from E-bay https://www.ebay.com/itm/Pico-PSU-120-12V-120Watt-DC-DC-ATX-Power-Supply-for-Mini-ITX-Mainboard/333192561048?hash=item4d93d30198:g:Z3QAAOSwfz9c1y7e.  I can't say if the E-bay ones are any good but the ones that I have look identical and came from a very demanding commercial application and I haven't found a bad one yet.  These plug directly onto the ATX power connector, connect 12 VDC to the input and away you go. They also have a cable with connectors to power the  hard drive and floppy drives.

Could this be adapted to work off both AC as well as battery, effectively making it a UPS setup?