Any way to put a 'UPS' after the PSU esp. on mini-itx?

[James Harris]

I'd like to set up a system that is small (mini-itx size), low powered
(as few watts as possible) and has battery backup.

Is there any product that supplies battery power but comes after the
PSU? I know it would have to supply different voltages and maybe that's
the reason I can't find such a thing. A traditional UPS would be no good
as wouldn't fit in to the same small case and I guess it would be less
efficient......

(Incidentally I tried with a laptop and all is fine except that the
Linux kernel doesn't recognise enough of the particular model I have in
order to control the fans - and they just keep whirring......)

 

[Bernard Peek]

I'd like to set up a system that is small (mini-itx size), low powered
(as few watts as possible) and has battery backup.

Is there any product that supplies battery power but comes after the
PSU? I know it would have to supply different voltages and maybe that's
the reason I can't find such a thing. A traditional UPS would be no good
as wouldn't fit in to the same small case and I guess it would be less
efficient......

There's a box that was on sale last week as a special in Lidl stores.
It's got a 7AH lead-acid battery and various low-voltage outputs.

 

[Rob Morley]

I'd like to set up a system that is small (mini-itx size), low powered
(as few watts as possible) and has battery backup.

Is there any product that supplies battery power but comes after the
PSU? I know it would have to supply different voltages and maybe that's
the reason I can't find such a thing. A traditional UPS would be no good
as wouldn't fit in to the same small case and I guess it would be less
efficient......

Mini-ITX machines run with a 12V brick PSU and a DC to DC converter, so
it should be pretty easy to add a rechargeable battery (with charging
circuit and switching) to power the DC converter when the external 12V
supply fails. Probably better to ask in an electronics group though.

 

[Dorothy Bradbury]

Yes...
o Use 12V DC-2-DC convertor for the Mini-ITX board
o Use an industrial 12V PSU with battery failover capability

The latter are commonly DIN-rail mounted with ability to charge
the connected battery. They are focused on extending the hold-up
time of a SMPS (ie, brown-out, sags) rather than a long term UPS.

Alternatively...
o Battery charger to SLA, Sealed Lead Acid Battery
o Mini-ITX 12V car power supply
---- regulates to 12V re battery charger (or alternator) in circuit
---- prevents over discharging of the battery
o Mini-ITX 12V DC-2-DC convertor

The problem in both instances is lack of shutdown functionality...
o That can be provided by mains fail relay & serial port interface

However, practically...
o Cost out the above
---- particularly if you require s/w shutdown
---- particularly re future resale value, spares & actual compatibility
o Cost out compared to an UPS
---- eg, APC BackUPS or Belkin Universal
---- cheap on Ebay, 7Ah is about 12ukp and will last a long time on a
Mini-PC
---- provides s/w shutdown, proven design, off the shelf & non-dedicated

You can fit a larger battery to small UPS, but...
o Most use undersized transformers re *continuous rating*
o They rely on battery size to effectively regulate thermal heating
o So it would not be wise to stuff a 32Ah SLA on a unit designed for 7Ah

That said, even a small UPS with 7Ah will provide a long run-time on
Mini-ITX.
An UPS primary capability is a) extend hold-up time during brown-outs/sags
beyond
that handled by the size of the primary electrolytic capacitors etc and b)
extend running
time sufficiently to effect a controlled shutdown without loss of data.

Multiple power outages can exhaust even a large UPS if they appear far
apart, since
there is a finite time for the UPS to recharge in each instance - often
overlooked

 

[Daniel James]

o Use an industrial 12V PSU with battery failover capability

I'm interested in this too ... where might one obtain such a beast? Are
there makes/brands/models to look for (or to avoid)? How much should one
expect to pay?

Where should one start looking for more info?

Cheers,
Daniel.

 

[Dorothy Bradbury]

o Use an industrial 12V PSU with battery failover capability

I'm interested in this too ... where might one obtain such a beast? Are
there makes/brands/models to look for (or to avoid)? How much should one
expect to pay?
Where should one start looking for more info?

Try RS Components & go through the various industrial PSUs...
o Specifically those that allow daisy-chaining (N+1)
o There are also options for effectively UPS capability

Note this is not particularly cost effective - you may need to find a
shortlist of possible solutions and wait on Ebay for (quite) some time.

 

[Odie Ferrous]

I'd like to set up a system that is small (mini-itx size), low powered
(as few watts as possible) and has battery backup.

Is there any product that supplies battery power but comes after the
PSU? I know it would have to supply different voltages and maybe that's
the reason I can't find such a thing. A traditional UPS would be no good
as wouldn't fit in to the same small case and I guess it would be less
efficient......

(Incidentally I tried with a laptop and all is fine except that the
Linux kernel doesn't recognise enough of the particular model I have in
order to control the fans - and they just keep whirring......)

Speak to someone called Guy Fawkes. He gets around a bit - a search in
uk.adverts.computers will find him - but he knows this sort of thing ad
infinitum.


OD

 

[Daniel James]

Try RS Components ...

Thanks. I was hoping not to have to go to such a blatant cash-sink as RS,
but if the options are limited ...

o Specifically those that allow daisy-chaining (N+1)

Why so?

o There are also options for effectively UPS capability

I'm not sure that I can parse that ... but UPS wasn't my main interest, I'm
looking for a AC-DC PSU that can feed multiple DC-DC PSUs. I'd probably put
a bog-standard mains UPS on the AC side.

Note this is not particularly cost effective ...

No, but compared with the cost/inconvenience of three of four separate
"brick" PSUs it may be bearable.

Cheers,
Daniel.

 

[Dorothy Bradbury]

o Specifically those that allow daisy-chaining (N+1)

Why so?

For redundancy...
o Industrial production line must not go offline due to PSU failure
o Some industrial PSUs specifically allow "daisy-chain" for redundancy
o If a PSU fails then the others seamlessly take over

I'm not sure that I can parse that ... but UPS wasn't my main interest,

Sorry a typo...
o A switched-mode PSU will allow a power brown-out of about 4-6 cycles
---- the duration of their ability to sustain output is called Holdup Time
---- typically measured as a few milliseconds
o Some Industrial PSUs allow a battery to be connected - creating an UPS
---- their intention is to create a far longer Holdup Time
---- probably limits on the size of the battery re recharge time

I'm looking for a AC-DC PSU that can feed multiple DC-DC PSUs.
I'd probably put a bog-standard mains UPS on the AC side.

In which case you use...
o Any suitable AC-to-DC PSU of the correct voltage & wattage rating
o Appropriate multiple DC-to-DC PSUs as required

Industrial PSUs handle single-output (eg, 12V) to whatever size you want,
they are also long life, high quality and handle sudden surges ok. Remember
3.5" HD startup current is quite high, and desktop opticals are also quite
high.

Ebay often has big 12V industrial PSUs - far more reliable than standard
ATX,
if you buy the type which can daisy-chain you can create PSU redundancy.

 

[Daniel James]

For redundancy...

Ah! Understand now. That would presumably be daisies chained in parallel? I
was thinking serial.

Thanks for the other advice ... yes, obviously I would need multiple DC-DC
PSUs (and they're not cheap compared with standard PC AC-DC PSUs) but they
are available as little daughter-boards that just push into an ATX power
connector and supply enough current for a mini-ITX board and a couple of
drives (varying models available between around 50-200W, so some have
plenty for a desktop HDD and DVD).

Ebay often has ...

Thanks, but (for reasons not relevant here) I dislike and distrust eBay and
its whole business model and won't tough them (or any other organization
trading in the same way) with the proverbial barge-pole. You must be able
to get these things through more conventional channels ...

Cheers,
Daniel.

 

[James Harris]

Mini-ITX machines run with a 12V brick PSU and a DC to DC converter,
so
it should be pretty easy to add a rechargeable battery (with charging
circuit and switching) to power the DC converter when the external 12V
supply fails. Probably better to ask in an electronics group though.

Have found some useful info there. Thanks.

 

[James Harris]

Bradbury wrote:

Thanks, but (for reasons not relevant here) I dislike and distrust
eBay and
its whole business model and won't tough them (or any other
organization
trading in the same way) with the proverbial barge-pole. You must be
able
to get these things through more conventional channels ...

I think there are other sites, e.g. http://www.ebid.co.uk - does that
have the part of the business model you dislike?

HTH

 

[James Harris]

Yes...
o Use 12V DC-2-DC convertor for the Mini-ITX board
o Use an industrial 12V PSU with battery failover capability

The latter are commonly DIN-rail mounted with ability to charge
the connected battery. They are focused on extending the hold-up
time of a SMPS (ie, brown-out, sags) rather than a long term UPS.

Alternatively...
o Battery charger to SLA, Sealed Lead Acid Battery
o Mini-ITX 12V car power supply
---- regulates to 12V re battery charger (or alternator) in circuit
---- prevents over discharging of the battery
o Mini-ITX 12V DC-2-DC convertor

The problem in both instances is lack of shutdown functionality...
o That can be provided by mains fail relay & serial port interface

Thanks for all the suggestions in your post.

If I understand them, those above seem too bulky for what I have in
mind.

However, practically...
o Cost out the above
---- particularly if you require s/w shutdown
---- particularly re future resale value, spares & actual
compatibility
o Cost out compared to an UPS
---- eg, APC BackUPS or Belkin Universal
---- cheap on Ebay, 7Ah is about 12ukp and will last a long time on a
Mini-PC
---- provides s/w shutdown, proven design, off the shelf &
non-dedicated

Some sort of mini PC is good. I've been looking at these. Some have a
PSU which will work in a car (dirty 12V supply) and from the mains via a
brick PSU which, presumably, puts out 12 or more volts and uses a small
switching dc-dc converter inside the case. That would be ideal if there
was some form of battery backup. Enough power to hibernate gracefully
would be fine for me - to avoid corrupting the file system.

Speaking of the file system, I would like to use a flash-IDE drive but I
think they may get damaged by repeated writes to the same place. Maybe
OK if not the system disk....... but that's off topic.

An UPS primary capability is a) extend hold-up time during
brown-outs/sags beyond
that handled by the size of the primary electrolytic capacitors etc
and b) extend running
time sufficiently to effect a controlled shutdown without loss of
data.

That's all I need. For mini-itx it shouldn't be too demanding but I
can't seem to find a suitable product - that will fit in the case.
Mini-itx car PSUs are available which will tell the PC to shut down when
the battery drops below 11v for a minute or so or when the ignition is
turned off but they don't seem to cope with total power loss.

As a slight aside, a nano-itx motherboard in a mini-itx case would leave
a little room maybe for a back up battery.