Uninterruptible Power Supply (UPS) Energy Efficiency?

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scdr
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Uninterruptible Power Supply (UPS) Energy Efficiency?

Post by scdr » Thu Jul 16, 2009 2:19 pm

Recently the battery in my APC Back-UPS 300 died (no longer holds enough charge to power my desktop).

I am trying to decide whether to replace the battery, get a new unit, or what.
(This is a home office computer in a city with pretty reliable power - just needs to power long enough to get over the occasional short power dip, or enough time to save work in a blackout.)

The replacement batteries are $40 from APC, though less expensive ones may be available from other names. (But don't know good brands.)

Replacement UPSs start at about $50 (one of those cases where most of what you are paying for is marketing/distribution/etc., and not the actual product, I guess).

How much power does a typical consumer grade UPS use?

Some of the newer UPSs make claims of "Greenness", but I haven't been able to find comparisons of how much power does a small UPS use, or comparisons of older models (Like the Back-UPS 300, or Back-UPS ES 500) with current ones. Are these Green claims just marketing fluff?
If newer UPSs are more efficient, how much (how much less energy use compared to older model)? Is it enough to make a significant difference in energy use in a typical home or office user setting, where most of the time the computer is off, computer is on for a few hours a day, and blackouts are rare.

(e.g., Would the power savings from a new unit offset the additional cost of the new unit?
Would it be greener to stick with the UPS I have and replace the battery - considering all the energy involved in manufacture/disposal/etc. of the UPS?)

My computer has an older power supply (Nexus NX3500) - less energy efficient. I have been considering updating to more efficient model.

Since a UPS is really just an AC-DC converter/battery charger/inverter and some switching, it seems like a poor design for today's PCs (since LCD monitors just need a DC supply). Seems like should do it AC-DC converter/battery charger/DC-DC converter (like a PicoPSU) to supply other computer voltages (and to power LCD). (Similar to the Google's servers
http://news.cnet.com/8301-1001_3-10209580-92.html
but adding an output for an LCD monitor and/or external hard drives. )
I found the battery charger unit sold by minibox, but it doesn't seem to be designed to work with the regular PicoPSU - e.g. needs higher input voltage.
Are there similar solutions where the pieces come together (so you don't have to piece everything together yourself)? Are there published examples where somebody has worked out the details of getting something like this to work.
How efficient would that be, compared to stand-alone UPS and power supply? How costly?

Thanks

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Re: Uninterruptible Power Supply (UPS) Energy Efficiency?

Post by MikeC » Thu Jul 16, 2009 3:35 pm

scdr wrote: (e.g., Would the power savings from a new unit offset the additional cost of the new unit? Would it be greener to stick with the UPS I have and replace the battery - considering all the energy involved in manufacture/disposal/etc. of the UPS?)
No to the 1st question and yes to the second. I just can't see your UPS drawing enough power that a new "greener" one would justify its mfg cost.
My computer has an older power supply (Nexus NX3500) - less energy efficient. I have been considering updating to more efficient model.
That's probably worthwhile if you go super efficient.
Since a UPS is really just an AC-DC converter/battery charger/inverter and some switching, it seems like a poor design for today's PCs (since LCD monitors just need a DC supply). Seems like should do it AC-DC converter/battery charger/DC-DC converter (like a PicoPSU) to supply other computer voltages (and to power LCD). (Similar to the Google's servers
http://news.cnet.com/8301-1001_3-10209580-92.html
but adding an output for an LCD monitor and/or external hard drives. )
Good points.
I found the battery charger unit sold by minibox, but it doesn't seem to be designed to work with the regular PicoPSU - e.g. needs higher input voltage. Are there similar solutions where the pieces come together (so you don't have to piece everything together yourself)? Are there published examples where somebody has worked out the details of getting something like this to work. How efficient would that be, compared to stand-alone UPS and power supply? How costly?
A UPS that delivers 12VDC + picoPSU would be ideal for what you're thinking about... but I have no idea whether such a device exists. It would probably be simple to make, at least for a PSU manufacturer.

pyotr
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Post by pyotr » Fri Jul 17, 2009 7:40 am

scdr wrote: Since a UPS is really just an AC-DC converter/battery charger/inverter and some switching, it seems like a poor design for today's PCs (since LCD monitors just need a DC supply). Seems like should do it AC-DC converter/battery charger/DC-DC converter (like a PicoPSU) to supply other computer voltages (and to power LCD).
There's a thing called PicoPSU which seems to do what you describe, with some caveats. The input must by 16-18V for the battery to charge, so you can't use the output of a ATX PSU. And its output can also exceed 12V, so you need one of the "wide input" PicoPSU's. And connecting your LCD would probably be out of the question too.

It's a nice idea, what is lacking IMO is the fact that there's no feedback to the system that it is running on batteries and / or how much power is left. So you can't do an automatic shutdown when the power is running out. IOW not suitable for a home server :(

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Post by Wibla » Fri Jul 17, 2009 10:15 am

Optimal charge voltage for 12VDC lead-accumulator batteries is 14.4V... not 16-18 :-)

mark19891989
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Re: Uninterruptible Power Supply (UPS) Energy Efficiency?

Post by mark19891989 » Sun Jul 19, 2009 5:25 am

MikeC wrote: A UPS that delivers 12VDC + picoPSU would be ideal for what you're thinking about... but I have no idea whether such a device exists. It would probably be simple to make, at least for a PSU manufacturer.
I would like a ups that give out 12v, because like said above, the dc/ac conversions are wastefull.

I already own 2 pcs with pico psus in them, so a UPS that gives out 12v, aswell as power sockets for the monitors would be perfect.
Last edited by mark19891989 on Mon Jul 20, 2009 10:26 am, edited 1 time in total.

proc
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Post by proc » Sun Jul 19, 2009 9:24 am

Pay attention to the fact that the output of the picoUPS is not regulated.

It is clearly stated on the picoUPS page of a reliable Italian online shop specialized in Mini-itx stuff, that you must use it with M1-ATX, M2-ATX, M3-ATX or picoPSU 6-24V, but not with picoPSU 120W.

http://www.mini-itx.it/controller-alime ... s-100.html

mark19891989
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Post by mark19891989 » Mon Jul 20, 2009 10:31 am

http://e.molioner.dk/projects/ups/ somthing like this seems suitable, uses this http://www.mini-box.com/picoUPS-100-12V ... kup-system

If i had money i would consider getting one.

Aparently there planing on releasing one that will charge at a lower input voltage, which would be more suitable.

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Re: Uninterruptible Power Supply (UPS) Energy Efficiency?

Post by dhanson865 » Tue Jul 21, 2009 5:07 am

MikeC wrote:
scdr wrote: (e.g., Would the power savings from a new unit offset the additional cost of the new unit? Would it be greener to stick with the UPS I have and replace the battery - considering all the energy involved in manufacture/disposal/etc. of the UPS?)
No to the 1st question and yes to the second. I just can't see your UPS drawing enough power that a new "greener" one would justify its mfg cost.
Mike is absolutely correct on the manufacturing cost making it not "worth it" for environmental reasons. Unfortunately you may find it worth it for cost of purchase reasons.

When I replaced my UPS last time I did so when a major retailer had them on sale for less than the cost of a replacement battery.

My rule of thumb is if the UPS costs less than $50 new (on sale or with or without rebate) I get a new one. If the UPS costs hundreds of dollars I get replacement batteries.

Now all of that only makes sense if you aren't in a hurry. If you want it quick it's easier to get a battery cheap in a hurry than to look for a deal from a retail source.

If you buy a battery from a local manufacturer / refurbishment shop you even save most of the costs of transportation and help your local economy (though you might not save any money this way).

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Post by DanceMan » Mon Aug 03, 2009 1:11 pm

on sale for less than the cost of a replacement battery.
This factor could be greatly different depending on the source. Locally here in Vancouver I would first check Polar Battery's Advanced Battery Specialties (on Boundary between 1st and Hastings) for a gel cell. Buying from any normal consumer retail outfit is likely to be a lot more expensive. There must be equivalents to ABS in other major cities, and online.

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Post by electrodacus » Sat Aug 22, 2009 7:26 pm

I just have an idea for your problem :) is just an idea but it can work and it will be low cost
I have some ATX power supply 120W and 130W that require 18V to 28V DC input all you will need is a charger and an 18V Li-ion battery depending on your requirements even a cordless drill battery can work.
see this post viewtopic.php?t=55084
I think I will use something similar for my computer I'm referring to Li-ion battery as UPS.

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Post by electrodacus » Sun Aug 23, 2009 12:35 pm

Ok I was thinking more and it will definitely work but it will work better with 6 cell Li-ion so the max voltage when full charged will be 4.2V x 6 = 25.2V just perfect for this power supply and the lowest voltage this power supply will work is about 16V this is 16V/6 about 2.66V per cell but you will need a comparator that will stop the power supply at about 3V per cell or 18V.
If you will use 2000mA cells you get about 40Wh so a PC with 40W will run for one hour from this small Li-ion battery.
I think I will build something like this for me even if I don't really need it seems as a good idea and is cheap.

scdr
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Post by scdr » Mon Aug 24, 2009 11:23 pm

Thank you for the link to article using the Pico-UPS
http://e.molioner.dk/projects/ups/
as I suspected, not as easy to use as it should be.

In general how efficient are DC-DC converters (e.g. stepping 12 volts up to 14.4 volts, or vice-versa)? I would have thought that since battery charging current doesn't usually have to be very high it would make sense to have the main converter change AC down to 12v DC. Then use a DC to DC converter in the battery charger to boost to battery charging voltage. The Pico-UPS approach of having main converter running to battery charging voltage, and then running all the power for the system through a DC to DC converter to drop to 12 volts seems like it might be wasteful. Or are DC to DC converters efficient enough that doesn't matter.

Using 12v for everything, but boost to higher for battery charging also makes it somewhat easier to power external devices (like LCDs, modems, routers, etc.) Certainly they use a variety of voltages, but 12v or 5v seem to be the more common levels.

Has anybody seen any projects that adapt a commercial UPS to this kind of application? Seems like one approach would be to use the UPS to charge battery and detect power loss, but bypass the inverter. (Of course that would entail separate AC to DC adapter for normal use, and would have to figure how to switch from that to battery power when power failed.)
Last edited by scdr on Mon Aug 24, 2009 11:46 pm, edited 1 time in total.

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Post by electrodacus » Mon Aug 24, 2009 11:43 pm

Yes I think that Pico-UPS is not a very good design is is really working as stated in the link.
DC to DC converters can be quite efficient it depends on the design and voltage difference the bigger the voltage difference the less efficient the converter is. Also the efficiency is dependent on designed max output vs the load. best efficiency is usually from 20 to 80% of the max designed output. The efficiency can be as high as 97% and as low as you want :)

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Post by fastturtle » Fri Jan 15, 2010 11:01 am

Answers IN order Asked:

1) Get the new Unit - Newer features = extra cost
2) Depends on how much is being drawn (system load)
3) Forget Green - Overpriced for little gain (marketing fluff)
4+5) Varies on the Efficiency Gains - See Answer 1 again
6) No - Green Costs do not justify replacement ($100)

To calculate green costs you have to factor in cost of making the unit plus the shipping costs (all of them) Rule of thumb is 2.5x the cost for Green Calculations when looking at replacing a working unit. They do not apply when considering new items.

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Post by OddSilence » Wed Feb 10, 2010 4:35 pm

scdr wrote:
Recently the battery in my APC Back-UPS 300 died (...).

I am trying to decide whether to replace the battery, get a new unit, or what.
:idea: On APC website it says that they have a "Trade-UPS" option, allowing the customer to give them his old UPS when buying a new UPS and receive a discount in the price (up to 25%).

I guess they'll recycle the old unit - and since they made it, they probabbly know how to recycle it well... If so, maybe that's a good option grean-wise.

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