# My APC Back-UPS ES500 did NOTHING when I had a blackout



## Sinjz (Jun 14, 2007)

Had a black out last night and when the power went down, so did my computer. The UPS did NOTHING except that it started to BEEP! [email protected]#$%^&. The beeping lasted about half an hour. Power was out for about 4 hour. When I finally plugged everything back in, I now get a "replace battery" warning beep from the UPS. It didn't signal anything before the blackout. BTW, my multimeter reads ~13.3 volts on the SLA battery, when I removed it. Is that about right? Anyway, should I upgrade, find a replacement battery or find someway to revive this battery? I repeat it didn't even give me a minute to shut down properly.  I assume it's all about the battery, but if my UPS is just too crappy, somebody let me know. :sigh:


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## Handlobraesing (Jun 14, 2007)

Sinjz said:


> Had a black out last night and when the power went down, so did my computer. The UPS did NOTHING except that it started to BEEP! [email protected]#$%^&. The beeping lasted about half an hour. Power was out for about 4 hour. When I finally plugged everything back in, I now get a "replace battery" warning beep from the UPS. It didn't signal anything before the blackout. BTW, my multimeter reads ~13.3 volts on the SLA battery, when I removed it. Is that about right? Anyway, should I upgrade, find a replacement battery or find someway to revive this battery? I repeat it didn't even give me a minute to shut down properly.  I assume it's all about the battery, but if my UPS is just too crappy, somebody let me know. :sigh:



Battery voltage only tells relative capacity. I had a few of those modern oversized power strip style UPSs and I've never liked them much.

Get something that looks like this:
http://www.upsforless.com/index.asp?PageAction=VIEWPROD&ProdID=30

Some of them have a lower VA rating, but don't be fooled. These older units have a bigger battery pack in most cases and since battery can produce more usable power when they're not heavily loaded, twice the battery capacity offers more than twice the runtime. 

My 450VA is a BackUPS from 1992 that I bought used and got new batteries for. It has a 12v 12Ah battery pack. Yours has 7.2Ah battery pack.


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## Eugene (Jun 14, 2007)

APC are usually good UPS units so I'll bet its a bad battery. Mine lasted about 5 years but I haven't gotten around to replacing it yet. Some of them have a fuse on the battery leads, check and make sure you have power at the circuit board and not a blown fuse. You haven't see a fuse blow until you see a spark and 200A fuse on a big ol UPS pop.


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## eluminator (Jun 14, 2007)

Am I allowed to chuckle, or would that be mean 

13.3 volts sounds good to me. If you are measuring it when it's not under load, you might try loading it. I would hook it up to the computer and pull the plug from the wall and see what the battery voltage is. 

Of course I don't have a UPS for my computer, and don't see the need. You might want to try a different load. Maybe some lamps would do.

I'd also check the wire connections going to the battery.


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## Sinjz (Jun 14, 2007)

Handlobraesing, my computer doesn't draw that much power. It's a pretty low end machine.... I dooubt I'm drawing more than 300 watts, so my UPS is suppose to be good enough. I'm not looking for long runtime. I just want 5 minutes, so that the computer can shut itself down properly. Beside don't have the $50 spare to spend on this right now. Of course it looks like the battery is gonna cost me $30, so maybe I will look. 

When I pull the plug from the outlet, I get one dying gasp of a beep and NO power at all.  Can't even get a clock radio to light up.  

Chuckling is mean!!! :mecry: Of course it might just be that constant beeping going on right now. I gotta shut my computer down cause this UPS is giving me a FREAK'IN headache!!!! 

I remember reading something awhile ago about someone using a car battery or something as his UPS. Anybody remember that? Link?

Anybody know of a single place I can get a new battery for this and my toothbrush to consolidate the shipping cost?


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## orionlion82 (Jun 14, 2007)

well, you are limited by input power from the battery and output power from the inverter. 

SLA batteries are the way to go and a car battery might not be the best solution. 
perhaps you can research manufacturers and look for more AH? 

i am betting your inverter is shot though. that or the regulation circutry...

i hear the APC models made for buisnesses and industry are far above howmowner/consumer grade ones, so i would look into those. 
i have heard good things about them from reputable people in comparison to the "everyday joe" ones

allso, your computer power supply might be the culprit. (known as a PSU)
most models made by fortron, emacs, zippy, silverstone, and PcP&c are known to be above most in terms of quality. 
(some antecs are good and some are not, so that is a trickier matter)


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## Handlobraesing (Jun 14, 2007)

Eugene said:


> APC are usually good UPS units so I'll bet its a bad battery. Mine lasted about 5 years but I haven't gotten around to replacing it yet. Some of them have a fuse on the battery leads, check and make sure you have power at the circuit board and not a blown fuse. You haven't see a fuse blow until you see a spark and 200A fuse on a big ol UPS pop.



The most economical thing maybe to get a UPS with the biggest battery you can find. This usually means you have to buy a higher VA capacity unit since they don't make lower VA rating one with a big battery pack. 

If you bought it based on acceptable runtime out of the box, you'd need to replace the batteries about every other year. The battery lives in harsh conditions. The temperature of battery pack while on continuous trickle charge is around 100F. 

If you significantly oversize the unit for considerably more runtime than you want, the batteries can deteriorate significantly more, but still provide a performance adequate to your need.


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## snakebite (Jun 14, 2007)

that unit may be subject to a recall.
seems they catch fire!
http://www.cpsc.gov/cpscpub/prerel/prhtml03/03068.html


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## Handlobraesing (Jun 14, 2007)

snakebite said:


> that unit may be subject to a recall.
> seems they catch fire!
> http://www.cpsc.gov/cpscpub/prerel/prhtml03/03068.html



Huh? That's the CS, not ES.


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## Torque1st (Jun 14, 2007)

Using the on/off switch on the front of my APC UPS unit does a battery test every time it starts up. It has been a few years since my battery was replaced and it occasionally fails the battery test. My APC UPS unit has worked flawlessly thru a couple of recent power outages tho.

I have three UPS units. I use two on my computers and one older low power unit for the cable modem and router.


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## Lite_me (Jun 15, 2007)

I run 4 UPS's. Two on Hi-def TV's, one on some components (VCR, DVR, Receiver, DVD) and one on my main PC. I've not had any problems with them. The oldest one is about 10 yrs. old. I recently changed the battery in that one. It wouldn't power the equipment more than a few minutes anymore. I have more power outages than normally acceptable on my street. I've complained and it has been getting better. Bad thing about that is, I don't need my flashlights as much anymore. :thinking: :shakehead


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## LuxLuthor (Jun 15, 2007)

Sinjz said:


> Had a black out last night and when the power went down, so did my computer. The UPS did NOTHING except that it started to BEEP! [email protected]#$%^&. The beeping lasted about half an hour. Power was out for about 4 hour. When I finally plugged everything back in, I now get a "replace battery" warning beep from the UPS. It didn't signal anything before the blackout. BTW, my multimeter reads ~13.3 volts on the SLA battery, when I removed it. Is that about right? Anyway, should I upgrade, find a replacement battery or find someway to revive this battery? I repeat it didn't even give me a minute to shut down properly.  I assume it's all about the battery, but if my UPS is just too crappy, somebody let me know. :sigh:



Sinjz, I feel your pain. Had the same situation happen in the past and it was the battery. Like others have said, if the batteries are not forced to power your PC which puts the real strain on them, they often continue indicating they are good. They usually last 3-5 years depending on use. If older than 5 years, plan on it being bad.

I had a series of talks with engineers at APC and read a bunch of sites before I began to realize how crappy and overstated many UPS brands and models really are. I typically bought mine at Staples. 

If you are like me, you sort of guessed at your actual needs rather than measuring the amps being drawn by your whole setup while plugged in and running. I have owned about 15 UPS's, and I have to laugh when I remember back to my early purchasing decision was based up the "seems about heavy enough when lifted" test. APC does have a decent website you can lookup your equipment and get a rough idea of what you need here.

I ended up getting one of these Sperry Digisnaps years ago for pretty cheap, and you plug everything into a powerstrip, turn it all on, then measure the current being used at full load while doing a couple of common tasks. This gives you a reliable indicator of what you need...then you add another 20-30% above that....then figure out how long you want to run without power and pick the model you REALLY need.

I ended up getting their APC Smart UPS 1500 which periodically puts the UPS into being used by your setup, shows how much of the load capability is being used of the UPS capability, and conditions the power coming into your house to smooth out spikes and drops. After about 3.5 years, my battery replace alarm came on, and I'm about a year into the new one.


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## Handlobraesing (Jun 15, 2007)

LuxLuthor said:


> Sinjz, I feel your pain. Had the same situation happen in the past and it was the battery. Like others have said, if the batteries are not forced to power your PC which puts the real strain on them, they often continue indicating they are good. They usually last 3-5 years depending on use. If older than 5 years, plan on it being bad.
> 
> I had a series of talks with engineers at APC and read a bunch of sites before I began to realize how crappy and overstated many UPS brands and models really are. I typically bought mine at Staples.
> 
> ...



If you have a serial port on your computer, make a cable(or buy one) for your SmartUPS. Using hyperterminal, you can get it to report how much the UPS is loaded in percent. Keep this well below 50%. Any higher and lead acid battery becomes inefficient and your runtime would be far worse than 1/2 the runtime of 50% load. 

Connect to it using hyperterminal @ 2400 bps/8N1
push shift+Y

shift+P reports load in percent
shift+B reports battery voltage

The SmartUPS lets you change battery transfer voltage as well as sensitivity to sags. 

(more commands here: http://www.networkupstools.org/protocols/apcsmart.html)


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## LuxLuthor (Jun 15, 2007)

That's pretty amazing. Gotta love [email protected]!


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## jrmcferren (Jun 15, 2007)

I don't know about APC UPSes, but my Powercom has a self-test function. The self-test can be activated on my Powercom in one of three ways (two of which are by software).

-Press the on/off button for about a half second.
-Press the self-test button in software
-A time set in software.

These self-tests allow the UPS to test the battery and the inverter as the load is placed on the battery for about 2-3 seconds.

I don't usually recommend stuff from Taiwan, but Powercom UPSes are good.


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## Handlobraesing (Jun 15, 2007)

jrmcferren said:


> I don't know about APC UPSes, but my Powercom has a self-test function. The self-test can be activated on my Powercom in one of three ways (two of which are by software).
> 
> -Press the on/off button for about a half second.
> -Press the self-test button in software
> ...



The batteries are good for at least a few dozen cycles of full discharge, so it's not a bad idea to do a full discharge with expected load connected. If the runtime is unacceptable relative to new state, it's time to replace the batteries.


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## barkingmad (Jun 15, 2007)

Was it overloaded or near capacity? 500va does not seem a lot if you have a PC and other things running off it? Was it just the PC running on it or a monitor, printer etc.

How old were the batteries? 

How old is the UPS?


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## orionlion82 (Jun 15, 2007)

you could cut out the batteries entirely and use one of these: 

http://www.genpropower.com/powerware_pf2_flywheel.htm

but its a bit spendy, and you would need some space. 

(they use them in industrial plants to keep systems running in brownouts and to handle loads while switching external power sources, before the generator kicks in, etc...) 

allthough i imagine you could make one in a better size for cheap enough...


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## turbodog (Jun 15, 2007)

I deal in this stuff for a living. Whether or not your battery or unit is bad, those units are pretty much junk.

Save a little $ and buy a used/refurb smart-ups off ebay. Any of the apc smart-ups series will last a lifetime. Their batteries are cheap to replace. They have much better self-test features, and most of them put of pure sine wave power.


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## OddOne (Jun 15, 2007)

I snagged a military-grade 1,500VA rackmount standby UPS off eBay several years ago that was used at a university and replaced with a newer model when it came due for batteries. It had a selling price of $3,400 at the time and included a line conditioner. I paid $80 + shipping for it and spent another $120 on batteries. (It takes SIX 7Ah gelcells in SERIES!) Recently put new batts in it as the first set I bought finally reached their life expectancy.

It runs my computer, monitor, stereo, router, modem, and desk lights for about two hours. 



Under typical conditions for a UPS, SLA batteries should be replaced every 5 years regardless of how many times the UPS went to batt power, as SLAs lose their capacity to produce appreciable current when they get old.

oO


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## daloosh (Jun 15, 2007)

When you guys talk about the SLAs getting old and replacing them, is that 3-5 years after putting them into service, or after they are manufactured? Reason I ask, is I bought a crappy lower end APC last year and never took it out of the box yet. 

thanks
daloosh


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## LuxLuthor (Jun 15, 2007)

daloosh said:


> When you guys talk about the SLAs getting old and replacing them, is that 3-5 years after putting them into service, or after they are manufactured? Reason I ask, is I bought a crappy lower end APC last year and never took it out of the box yet.
> 
> thanks
> daloosh



That's a good question. If someone here (i.e. Turbodog) doesn't know for sure, that would be a good thing to call and ask APC Tech support. There is obviously some time related deterioration of the electrodes from the acid, but I'm assuming it is more directed at once you start using it (within reason).


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## Sinjz (Jun 16, 2007)

Why do you think the inverter or regulation curcuitry is shot? How can I tell if it is? BTW, CoolMax PSU. How do they rate? Printer (was off) is on a different power strip.

Oh, I get what Handlobraesing is saying now. Less drain = longer battery life. For me though, I haven't had a blackout since the NorthEast blackout of 2003, and my UPS worked then! That being the case, I don't think I'm actually draining the battery. Am I wrong? 

ES 500 not CS.  Not that I know the difference. I just know they won't gimme a free replacement. 

Lux, tried the UPS selctor and the 'best price' catergory came up with a UPS very similar to mine 550 VA; My particular model has been discontinued. :shrug: I think I'm okay for the short runtime I want.

Just have the computer and a monitor hooked up to it. Got a external USB drive connected to the UPS too, but ti was off at the time, as were my powered speakers.

Turbodog, would I need all the self test and nice sine wave stuff for my limited use?

OddOne, that sounds cool! I'm sorta getting the itch to try that, but again, i RARELY ever get blackouts here.

Hey, is there any way I can hook up a large car battery (or something similar) to my current UPS and get a LOT of runtime in case of a black out and still have the surge protection and somehow get my unit to charge the large battery?


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## barkingmad (Jun 16, 2007)

turbodog said:


> I deal in this stuff for a living. Whether or not your battery or unit is bad, those units are pretty much junk.
> 
> Save a little $ and buy a used/refurb smart-ups off ebay. Any of the apc smart-ups series will last a lifetime. Their batteries are cheap to replace. They have much better self-test features, and most of them put of pure sine wave power.


 
I agree APC Smart-UPS are good - but not perfect either - arrived at the office the other day to find one nice bubbling away and venting fumes - so hot it could hardly be touched.

Yes they do run self-tests but obviously something had gone wrong with this one. Although to balance it up - they are generally very reliable and APC do still make good UPS units.


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## orionlion82 (Jun 16, 2007)

oh. i see how it is now. 

if the last blackout was in 2003 and its been used twice and died, a UPS might not even be a good investment in the first place, let alone spending more to keep one going. it might have been dead for 2 years allready! 
begs the question, do you really need it? 

you have an external USB drive (for backups, right?) 
if the computer really is that old, the hard-drives will be nearing the MTBF if not allready exceeding it. 

the insurance of a UPS and any time or money you throw at it dosnt sound like its too well justified, especially of the hardware is as old as it sounds. 

i cant speak to your model of PSU 
but a test of one of their more recent enthusiast units was only fair. 
EDIT: note the lack of UL certification and lack of UL number (scary for something that makes 850W DC _no- wait the high power PSU's today really cant get UL because the amperage they are capable of exceeds obsolete standards_) and how the first test subject simply screeched and died in mid test. 

set aside the money you would spend with the UPS issue now, and add it to the "ups fund" for when you buy your next computer . you would allso be served well by a premium power supply in the next machine with correctly sized output for your hardware. 
poke around in the *articles* and *reviews* section of that link i sent to learn more. (keep in mind though the website is targeted at high powered gaming computers and enthusiasts, so its the right idea, but on a grander scale that what most people need)


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## Handlobraesing (Jun 16, 2007)

daloosh said:


> When you guys talk about the SLAs getting old and replacing them, is that 3-5 years after putting them into service, or after they are manufactured? Reason I ask, is I bought a crappy lower end APC last year and never took it out of the box yet.
> 
> thanks
> daloosh



The battery will last a long time, provided you occasionally plug it in and never let the state of charge come low.

SLA degrades more rapidly in UPS service, because the float voltage is kept relatively high to maximize usable capacity, but higher float voltage promotes electrolyte loss and raises temperature.

Higher temperature always mean accelerated deterioration. If you won't use your UPS for a while, plug in overnight every six months or so, then unplug.


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## binky (Jun 17, 2007)

Kinda in the same idea as many of the other posts...

I consult on IT and highly recommend the APC stuff, and I've had only great experiences with their responsive service. HOWEVER, for years I have been selling and recommending the Smart-UPS series. Never had a problem with them.

I started going downward on the product line in sympathy for the salon or very small offices. Within a 2 week span I had 2 of the ES series (both BE750BB) go bad. One was in service and I hadn't noticed but the darned thing came faulty with some of the surge-only ports simply not putting out any power at all; like they were disconnected. Just terrible. 

I'm going back to only recommending the SUA1000<XL> or better and not dipping much farther down the product line. Since the purpose of these is reliability, it'd be irrational to skimp to the level of increased risk. The only thing I'll buy in their lower level "PC & Workstation" line is the awesome HS 500 which is a low-demand unit designed for plugging in your router, cable or DSL modem, etc and gives you a built-in Ethernet port and web access to restart the outlets, all for around $200 bucks.


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## Lunal_Tic (Jun 17, 2007)

Doesn't the ES come with a USB port and software that automagically shuts down the computer?

-LT


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## gadget_lover (Jun 17, 2007)

jrmcferren said:


> I don't know about APC UPSes, but my Powercom has a self-test function. The self-test can be activated on my Powercom in one of three ways (two of which are by software).
> 
> -Press the on/off button for about a half second.
> -Press the self-test button in software
> ...




I have 5 different brands of UPS in the house and I'm very cautious about doing self tests. If it puts the load on the battery and the battery is bad, you crash your computer. Marginal batteries can read the proper voltage without load, but fall to nothing when a load is placed on them. I've had that happen. More than once.

I DO believe in UPSes. I run a computer 7x365.25 for the last 7 years that has virtually no problems. The UPS has a power conditioner that compensates for voltage dips as well as providing emergency power. Clean power is part of the trinity that gives good, dependable computers. Constant temperature and clean air are the other two.

Daniel


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## TedTheLed (Jun 17, 2007)

if you want the ups to work only once or twice for a minute or two while you shut down every few years, why have a rechargeable battery at all?

10 alkaline D-cells would work (the inverter should handle up to 15 volts or so..) and last longer. Especally if you got lithium Ds..


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## HammerSandwich (Jun 18, 2007)

I've had an APC ES let a PC go down during a power glitch. Not sure exactly what happened, because the UPS was almost new, and it has kept that same PC (and others) running in other situations.

That said, the ES models are definitely low-end.

I was just recently dismayed by a new ES750 that a neighbor ordered with a new Dell. Either APC has _really_ cheaped out on these UPSes, or else Dell got a special cut-rate model. The stupid thing has no USB (or serial) port to tell the PC to shut down!

I have been very pleased by Belkin's units, especially for the money. Belkin's software annoys me, but the UPSes work. The "network" UPSes are very, very solid. And the prices are reasonable with the hey-that's-the-combination-to-my-luggage (enter "12345" for 40% off) coupon code.

Has anyone used a new Tripp-lite lately? They used to make quality stuff.


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## eluminator (Jun 18, 2007)

I've had computers at home for 25 years. I've never had one go bad. I have two running 24/7 except they are on standby half the time. 

All I use is a surge suppressor.

The only machine I ever saw get clobbered by a power failure was an old Dell running NT 4 that I used at work. I accidentally kicked the power switch on the surge suppressor/power strip and NT needed to be re-installed. Those Dells using FAT32 had other problems. They finally wised up and switched to NTFS.

Heh heh, maybe I'd be better off without the surge suppressor too.

Maybe the PC power supply makes a difference. My two active computers and my two retired ones all use Seasonic power supplies. I use them because they are quiet as a mouse, but I think they are pretty good in general.


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## Handlobraesing (Jun 18, 2007)

Ditching the CRT for LCD makes a big difference.


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## turbodog (Jun 19, 2007)

The batteries age from date of mfg. They age faster when subjected to heat, as has already been said. They also age faster when at less than full charge.





LuxLuthor said:


> That's a good question. If someone here (i.e. Turbodog) doesn't know for sure, that would be a good thing to call and ask APC Tech support. There is obviously some time related deterioration of the electrodes from the acid, but I'm assuming it is more directed at once you start using it (within reason).


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## turbodog (Jun 19, 2007)

You might not really need the self-test and sine-wave output, but the smart-ups series bring other things to the party. In particular, it will shut down the pc AND the ups before the battery completely dies, thereby preserving battery longevity. It will also force the battery to reach a certain level of charge after an outage before powering the pc back on. This allows the unit to have time to do a shutdown if the power fails again, which often happens as power is coming back on.

The series also has MUCH better venting to keep the batteries cool. Automatic fans are also standard equipment.

The units cost more on the front end (except when bought secondhand off ebay), but are cheaper to run because they don't kill the batteries every time you turn around.

Also, almost forgot, they have something called smartboost and smarttrim. It allows the ups to correct for brownout voltages WITHOUT going "on battery". Again.... this all contributes to battery longevity.

And finally, an anecdotal tale: I was awakened one morning about 5 a.m. by my ups beeping. I check it and it was running in smarttrim mode, correcting for too HIGH AC voltage. I checked the outlet with a meter and found almost 150 volts. I called the power company, and was able to save some of my house's electrical stuff as a result. Turns out that the substation had a malfunction and was systematically increasing the voltage about every 15 minutes.

FYI: most ups supplies continue to draw battery power when shut down and unplugged. THAT is what kills a lot of batteries. You MUST unplug the battery if you want it to really turn off. AFAIK all smart-ups series have a handy plug on the back to accomplish this (without having to crack the case open).






Sinjz said:


> Why do you think the inverter or regulation curcuitry is shot? How can I tell if it is? BTW, CoolMax PSU. How do they rate? Printer (was off) is on a different power strip.
> 
> Oh, I get what Handlobraesing is saying now. Less drain = longer battery life. For me though, I haven't had a blackout since the NorthEast blackout of 2003, and my UPS worked then! That being the case, I don't think I'm actually draining the battery. Am I wrong?
> 
> ...


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## Handlobraesing (Jun 19, 2007)

Battery becomes less efficient when it is pushed near the limit.

Transformers(which steps up the battery to 115v) becomes less efficient when pushed harder as well.

Your ES500 and my BK450 are both rated for 300W output. The difference is how they assigned power factor. They assumed 66.7% on mine, 60% on yours, so while the real capability (watts) are the same, yours shows off a higher VA tag.

My 450VA Back UPS(March 1993):
300W (8 minutes)
150W (~24 minutes) 




I just ran a 150W light bulb on it and it ran for 23 minutes before low battery alarm was set off. The battery was installed in 2004, but the unit isn't in use right now. 

Almost 9 years later, it got far worse. They realized battery is one of the most expensive component, but inverter parts are going down in price, so they were able pair a smaller battery with a 500VA inverter, but in the end, you get about half the runtime. 

To get a runtime comparable to older UPS, you'll have to probably get a 1,000VA inverter, not for the extra inverter capacity, but for the larger battery it comes with. This is what happens in a consumer spec war. 

Your 500VA Back UPS ES(Nov. 2001): 
300W (full load) 4.1 minutes
150W (half load) 14.7 minutes 





Battery loses its ability to sustain voltage under load with age. Obviously, higher loads are more difficult to sustain. So, under the same load, smaller battery that's pushed harder needs to be in better conditions than a larger battery with greater capacity.


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## TedTheLed (Jun 19, 2007)

... what's a D cell? 4 amp hours? X 12 volts (with 10 cells you get more like 15 volts at first) = 48 watts for an hour, 96 watts for 1/2 an hour, 192 watts for 15 minutes..etc...not too bad for a $10.00 investment.. they last for years, and you can check their capacity more easily than sla batteries..
also, sinewave inverters use significantly less power to run than modified-sinewave..


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## Handlobraesing (Jun 19, 2007)

TedTheLed said:


> ... what's a D cell? 4 amp hours? X 12 volts (with 10 cells you get more like 15 volts at first) = 48 watts for an hour, 96 watts for 1/2 an hour, 192 watts for 15 minutes..etc...not too bad for a $10.00 investment.. they last for years, and you can check their capacity more easily than sla batteries..
> also, sinewave inverters use significantly less power to run than modified-sinewave..



192 watt @ 90% efficiency =213W/11v(because, battery won't hold 12v under that kind of load) 19.4A.

There is no way in heck a D cell would tolerate that kind of load, even for one second.


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## TedTheLed (Jun 19, 2007)

are you saying ONE D cell won't sustain that load? (in which case you would be correct), or 10 D cells? (in which case you would not)

10 D cells would be the same as nominal 12 volt 4 amp hour battery (only higher voltage at first) .. 192 watts may be pushing it, but I think is still within the realm of possibility, but a computer probably wouldn't draw that much anyway..


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## jrmcferren (Jun 19, 2007)

The only time you need a true sine wave is when you are powering devices like stereos. Anything else will handle the modified sine wave OK. Computers are actually more efficient on modified sine wave then on sine wave due to the nature of the power supplies.


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## TedTheLed (Jun 19, 2007)

sinewave inverters convert dc to ac much more efficiently than modified sine-wave. 
how a msw can run a computer better than a sw I don't understand.


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