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 Post subject: APC/UPS voltage drops
PostPosted: Thu Feb 09, 2006 12:14 pm 
Little Foot
Little Foot

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Location: north carolina
We've had several computers fry out on us the last few months so I crawled underneath the desk to check out the apc voltage drops after the last one. One unit is a belkin 1200ma unit with a liquid cell. That's the one I checked. I get 120 volts thru the battery outlets when I'm hooked up to household power. This is the same voltage as household power which strikes me as a little odd since we run a little high on voltage at this location. I would've expected the unit to put out closer to 115vac while hooked up and when disconnected.

Upon disconnecting the unit from the household current - my voltage drop across one battery outlet was 90vac and another was 95vac. I'm of the opinion that the unit is shot and may've contributed to the motherboard failure by allowing a spike to get thru.

comments?


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 Post subject:
PostPosted: Thu Feb 09, 2006 1:49 pm 
Northwood
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The voltage coming out of the UPS should be the same as the wall plug(when it's hooked up to household power). UPS's aren't 100% efficient but 90vac is low, sounds to me like it's time to change the batteries.

How old are the units?


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 Post subject:
PostPosted: Thu Feb 09, 2006 2:15 pm 
Team Member [Top 500]*
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I dunno about a spike but the 90 VAC is low for what it should be delivering. Typically in the 115 - 120 VAC range.

Quote:
Upon disconnecting the unit from the household current - my voltage drop across one battery outlet was 90vac and another was 95vac. I'm of the opinion that the unit is shot and may've contributed to the motherboard failure by allowing a spike to get thru.


You don't mention if the UPS was under any load? If you are getting the 90 VAC off an unloaded UPS that is not good. Have you checked the battery voltage when the unit is running and unplugged?

This is a typical specification for a basic ATX PSU:
Quote:
3.1. AC Input
Table 1 lists AC input voltage and frequency requirements for continuous operation. The
power supply shall be capable of supplying full-rated output power over two input voltage
ranges rated 100-127 VAC and 200-240 VAC RMS nominal. The correct input range for
use in a given environment may be either switch-selectable or auto-ranging. The power
supply shall automatically recover from AC power loss. The power supply must be able to
start up under peak loading at 90 VAC.
Table 1. AC Input Line Requirements
Parameter Minimum Nominal+ Maximum Unit
Vin (115 VAC) 90 115 135 VAC rms
Vin (230 VAC) 180 230 265 VAC rms
Vin Frequency 47 -- 63 Hz
+Note: Nominal voltages for test purposes are considered to be within ±1.0 V of nominal.


If the UPS in question was only delivering 90 VAC that is bottom end. If the 90 VAC you measured was unloaded UPS voltage that sucker is scrap! I would look at the battery voltage with the UPS under a load. Not a computer either but maybe a few 100 watt household lamps.

Ron


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 Post subject:
PostPosted: Thu Feb 09, 2006 5:42 pm 
Little Foot
Little Foot

Joined: Wed Oct 27, 2004 5:47 pm
Posts: 158
Location: north carolina
no, it wasn't under a load. I guess I kind of figured if someone heard me referring to "voltage drops" instead of "output voltage" they'd also figure I knew enough to do it without something dragging voltage off in series.
:)

I called belkin and they confirmed that the bat's are likely bad. The units are about three years old. They also informed me that a spike big enough to get through that unit would destroy the unit so for all intents and purposes - it's in working order.

Thanks for all the help.


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 Post subject: Re: APC/UPS voltage drops
PostPosted: Fri Feb 10, 2006 9:34 pm 
King of All Voodoo2 Cards
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Joe blow wrote:
One unit is a belkin 1200ma unit with a liquid cell.


You should see if you can get the gel cells for that thing. They're a tad heavier but they seem (at least, to me) to last a lot longer.

I also replaced the battery on my motorcycle from an electrolyte cell to gel cell and it's never given me a problem (unlike the two previous ones that dried up).


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