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Author Topic: Computer UPS to power radio power supply?  (Read 14637 times)

AB8OJ

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Computer UPS to power radio power supply?
« on: September 26, 2002, 09:30:27 PM »

I'm fairly new to the world of emergency power, so please bear with me if this is a silly question.

I've been wondering if I could use a suitably-sized computer UPS unit to power my shack's power supply when I lose AC power.  My thought is to plug the power supply (Diamond GZV4000 40A switching model) into the UPS's AC outlet, just like I'd do with a computer.

If this won't work for some reason, please explain why (but remember I'm new to this :-).  If it's workable, how would I go about sizing the UPS?

Thanks for the help, and 73!
-Ed-
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KG4RUL

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Computer UPS to power radio power supply?
« Reply #1 on: September 28, 2002, 08:24:59 PM »

With the UPS you are paying for a power supply which supplies DC power which is used to charge batteries which are supplying DC power to an inverter which supplies AC power to your existing power supply which supplies high current DC power to the rig.  Kind of like going from Detroit to Cleveland by way of Houston.  

You might be better off using your existing power supply to float charge a set of sealed lead acid batteries and then using the DC power from them to power the rig.  Your power supply capabilities would only be limited by the number of batteries you add to the system.

Dennis - KG4RUL
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N8EMR

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Computer UPS to power radio power supply?
« Reply #2 on: September 30, 2002, 08:05:15 AM »

Get a couple of deep cell batteries and a floating battery charger. Much more simple design.
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KG4RUL

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Computer UPS to power radio power supply?
« Reply #3 on: September 30, 2002, 10:01:13 AM »

If you are going to power the radios from the batteries and float charge them at the same time, a battery charger is not the way to go.  The output of the charger is not nearly clean enough for this purpose.  You would need to build a filter to use with it.  

Better to build a float charge circuit that utilizes the, pure, DC output of your existing power supply.

Dennis - KG4RUL
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INITZERO

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Computer UPS to power radio power supply?
« Reply #4 on: October 01, 2002, 06:29:09 PM »

>  if I could use a suitably-sized computer UPS unit to
> power my shack's power supply when I lose AC power

Short answer: Yes.

Medium answer: Yes, but that isn't the most efficient way. The UPS is converting 120V to 12V to charge the battery then 12V to 120V to your power supply which
converts 120V to 12V for your radios. Every time you
step up or step down the voltage, you lose a bit. It would be like if you were a bar tender mixing drinks.
Every time you pour from one glass to another, you
lose a bit of liquor. Not much, of course, but it
does add up.

My answer: If your computer UPS uses a 12V/13.8V
battery, it might be worth your time to open it up
and pull power for the radio directly from the
battery. That is what I do and it works well. I
have a fairly hefty UPS that I use for my computer,
network and phone systems. I don't want to get a
separate battery system for my 13.8V ham gear so I
just suck power off the battery before it goes
through the inverter. The UPS does a find job of
keeping the battery charged and I don't suffer from
an extra two conversion steps.

Matt (k4mls)
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WB2WIK

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Computer UPS to power radio power supply?
« Reply #5 on: October 02, 2002, 12:44:06 PM »

Remember that UPS's have three drawbacks:

-They're heavy and expensive

-They contain a switchmode power inverter that can (and often does) generate RF noise that can be heard in amateur receiving equipment

-And most of them, unless very large, very heavy and extraordinarily expensive, won't power your amateur gear and 40A power supply very long at all!

The typical UPS that you can lift and carry around will provide 300W for 10 to 30 minutes, if you're lucky.  The ones that will provide more than this (more power, or longer time period) get big.  An "emergency" such as fire, flood, earthquake, hurricane, tornado...or even a trainwreck, etc that happens to take out the local power lines...can last several hours to several days (or even weeks) to clear up, before utility power is restored.  A UPS that provides "emergency" power for 30 minutes isn't going to help when minute #31 rolls around.

UPSs are great for isolating your equipment from temporary spikes, surges and brownouts -- and that's what they're for.  For true "emergency power" for radio equipment, I'd go for something else.

WB2WIK/6
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AB8OJ

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Computer UPS to power radio power supply?
« Reply #6 on: October 02, 2002, 12:58:45 PM »

Thanks to all for your replies.  I failed to mention that I have free access to an older 1000VA UPS, which is how the whole thought process got started.

Cost notwithstanding, though, it sounds like it wouldn't really be a whole lot of use as is, given the points mentioned about (lack of) efficiency, noise generation, and "run time".  However, I like Matt's suggestion of drawing power directly from the battery if it's the right voltage, and I may look into that further.

Ed - AB8OJ
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K2GW

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Computer UPS to power radio power supply?
« Reply #7 on: October 02, 2002, 03:59:40 PM »

Two thoughts.

First, while somewhat inefficient, supplying AC to your 12 VDC power supply from a UPS is incredibly easy to do (takes about 30 seconds), and extremely inexpensive if you have access to a free old UPS.  I know; I've done it exactly like that myself.

Second it's pretty easy to add a large, external 12 VDC gell cell to most UPS's to provide a direct source of 12 VDC to your rigs while still providing AC power through the UPS's inverter to your computer.  Check out the 2002 ARRL Handbook which shows how to do it.

Finally, using Anderson 30 Amp Powerpoles for all of the 12VDC connections on your setup gives you more flexibility to move things around or use the 12 volt battery for field day or at a shelter.

73

Gary, K2GW
SNJ SEC
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WB2WIK

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Computer UPS to power radio power supply?
« Reply #8 on: October 02, 2002, 07:19:33 PM »

Ed, you might check into what that "1000VA" really means.  8.3A at 120Vac?  For how long?  1 minute?  10 minutes?  1 hour?

A "VA" rating, like a "Watt" rating, doesn't mean much when it comes to power storage.  Unfortunately, even a "Watt-hour" rating doesn't mean much, unless the rating corresponds to available current for a time period.

My "1500VA" UPS won't power my ham station for more than about 15 minutes.

WB2WIK/6
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AB8OJ

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Computer UPS to power radio power supply?
« Reply #9 on: October 07, 2002, 04:24:31 PM »

Gary, thanks much for the pointer to the Handbook.  Looks like a nice project for a cold winter weekend (coming a little too soon, I think).  (Especially considering the next point.)

Steve, I agree about the VA rating alone being pretty useless.  APC does have a runtime calculator on their web site, and for this model (SmartUPS 1000) a 300W load gets 17 minutes of runtime, while a 600W load gets a whopping 7 minutes.  That's assuming a steady load, of course, so my mileage would vary in a big way.

-Ed-
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Computer UPS to power radio power supply?
« Reply #10 on: November 03, 2002, 11:16:11 AM »

I can't believe the answers you are getting.  If you already have a ups, then use it!
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K3UOD

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Computer UPS to power radio power supply?
« Reply #11 on: November 04, 2002, 11:06:01 AM »

While not a good solution for running your rig, the UPS may be handy for running small station accessories (rotator perhaps) that require 120VAC.  Also, a small flourescent lamp plugged into a UPS can supply emergency lighting for quite a while.  A small soldering iron, or even a drill motor could be used to make repairs during a black out.  A large UPS could come in handy for many reasons.
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N4HRA

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Computer UPS to power radio power supply?
« Reply #12 on: November 05, 2002, 02:57:46 PM »

Since I work for a UPS mfg as a Field Engineer and provide Technical Support For customer and Field engineers let me add my 2 cents:
(1) Do not pull power off one of the batteries in the UPS system. the batteries are connected in series and this wil creat a inbalance in current to the batteries when power is returned and the charger starts recharging the batteries, also it will reduse your UPS run time
(2) UPS systems have 3 ratings a VA, watts and PF The va rating is the rating of the UPS, the Watts is the power the unit can supply, and the Pf is the power factor rating. SInce most UPS systems are rated for a pf of 0.8 the Watt of the UPS system is a product of VA rating and the PF rating. ie 1000VA X .8pf = 800W unit. Most computer have a power factor of .98 so if a UPS can produce 10amps @ .8pf the max current that can be drawn by a .98pf computer would be 8.1amps because of the power factor differance.
(3) Back-up run time is a calication of:
    (a) VA*Power factor = Adj Watts
    (b) Adj Watts/ Inverter Effency = Watts Required
    (c) Watts required/No of cells = Watts per cell
    (d) then you find the watts per cell on the battery mfg data sheet and thatwill tell you how long the ups will run untilit hits end battery
It would be best to run the ham station off it own battery system and items that require 120vac off the UPS system
Hope this helps some
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K2GW

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Computer UPS to power radio power supply?
« Reply #13 on: November 08, 2002, 02:23:35 PM »

N4HRA writes:

(1) Do not pull power off one of the batteries in the UPS system. the batteries are connected in series and this wil creat a inbalance in current to the batteries when power is returned and the charger starts recharging the batteries, also it will reduce your UPS run time.

That's correct.  The modification from the 2002 ARRL Handbook that I mentioned is for UPS's that have internal 12 Volt systems, not those with 24 volt or higher voltage internal circuitry.

73

Gary, K2GW
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KP4HE

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Computer UPS to power radio power supply?
« Reply #14 on: December 01, 2002, 11:47:48 AM »

UPS?? For what? Consumer Electronic UPS are for instantaneous power loss and DATA can be saved before SHUT DOWN and error free Boot Up when power is restored.  They are expensive and heavy.  Don't throw away your money on this for emergency power unless your backing up your computer.  12V Battries is the way to go.  Have them on  a cycle charger with any type of disconnect connector which you can connect you radio or "INVERTER" (most all new radios operate on 12VDC or have a 12V terminals).  Connect it to your radio when needed and disconnect it when not.  "You can call again the station or resend your message if you loose power for a long period of time.  If it's just momentanious just keep on going.  You should always have a surge protector on you power inlet.  Or just buy a Small Gas Generator.  Remote stations are a different story because there is nobody at the site to do the change over.
David
KP4HE
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