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Observations on a UPS - follow up to a previous post
"Doc" wrote in message
oups.com... On Aug 12, 10:24 pm, "James Sweet" wrote: A test to find out how long it will actually run the computer sounds like a good idea. That's a good way to kill the battery, these things tend to really punish batteries, after a few complete cycles they're often pretty well toast. You should be fine to try it for a bit, say 5 minutes without issues. Seems I've heard an occasional complete drain-down and recharge will extend the life of a rechargeable battery, that being constantly partially discharged and recharged is what shortens their life. Not so? Does it depend what kind of rechargeable it is? It does depend on the battery. Early Lithium-Ion batteries benefitted from the occassional full discharge, and Nickel-Metal Hydride batteries may benefit from it. Lead-Acid batteries (like is in your car) have major issues if they are completely drained, these are also the common battery in cheap, well, just about everything. Newer Lithium-Ion batteries and Nickel-Metal Hydride batteries have the controls in place so they don't benefit from a complete drain. The Lithium-Polymer batteries that are beginning to appear in some places do not benefit from complete drains, nor do they have problems with overcharging, and now that they've gotten the self-ignition problems eliminated look to replace just about everything but lead-acid. So know your batteries, and you know the necessary behaviors, but really the only problem ones are Lithium (non-rechargable) and Lead-Acid (damaged by full drain). Joe |
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Observations on a UPS - follow up to a previous post
In comp.sys.ibm.pc.hardware.misc James Sweet wrote:
A test to find out how long it will actually run the computer sounds like a good idea. That's a good way to kill the battery, these things tend to really punish batteries, after a few complete cycles they're often pretty well toast. You should be fine to try it for a bit, say 5 minutes without issues. Maybe, but a lot of people seem to swear by the Kill-A-Watt meter, which can be had all day for around $25 online, eBay etc. EE friend of mine compared one to a $2500 power analyzer at work, found that the Kill A Watt performance is pretty much inline with the specs printed for it. It's not as good as the professional equipment, but it's really very impressive for what it is and certainly adequate for consumer use. The wonders of modern microelectronics, it's amazing what they can do with one inexpensive chip and a handfull of passive components. I still remember when a pocket calculator was $300, then a few years later $50 would buy one just as effective, and not long after that they were under $20 and those are all more capable than large machines costing many thousands just a few decades earlier. Hmm. Interesting. I trust he did this right and tested non-ohmic loads such as a PC PSU as well? Arno |
#13
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Observations on a UPS - follow up to a previous post
Seems I've heard an occasional complete drain-down and recharge
will extend the life of a rechargeable battery, that being constantly partially discharged and recharged is what shortens their life. Not so? Does it depend what kind of rechargeable it is? You're thinking of nickel-cadmium batteries. The lead-acid batteries used in these power supplies can be crippled or destroyed by a "full" discharge. Try to avoid it. |
#14
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Observations on a UPS - follow up to a previous post
In comp.sys.ibm.pc.hardware.misc Doc wrote:
On Aug 12, 8:45 pm, "William Sommerwerck" wrote: My experience -- at least where I live -- is that the power is off for a fraction of a second, or hours. There's rarely anything in-between. In general, I'd say that's my seat of the pants impression too, though not always. I also notice they'll often come in clusters. The transformer - if that's the correct term for it - big gray basically cylindrical unit on top of a power pole - near my house blew once. Ugh. Putting them up for each individual hous is a very, very historic way to do it. Powerful **BOOM** and a huge column of flame. Not sure what the fuel for the flame was, do they have oil in them? Yes, for cooling. If it was an old transformer, you might have giotten a nice load of Dioxins for free there... Also a bit disconcerting since anyone nearby surely would have been in jeopardy from flaming debris. The right way to do this is to use bigger transformesr for 10-100 houese and to bury 3-phase AC lines. A lot more expensive, but pays off in the long run, since you have less problems. And all these ugly poles and transformers will vanish. Needless to say, power was out for a while on that one. I can believe that. Arno |
#15
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Observations on a UPS - follow up to a previous post
Lead-acid batteries (like is [sic!] in your car) have major issues
if they are completely drained, these are also the common battery in cheap, well, just about everything. The _only_ consumer products I've owned that used lead-acid batteries were an early Sony Discman, and two APC SPSs. They are not common in consumer products. They provide relatively high capacity at a low cost (which is why they're used in SPSs and UPSs), but they are too-easily damaged by a full discarge. I accidentally ruined a $45 batter for the Sony D-T10. |
#16
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Observations on a UPS - follow up to a previous post
My experience -- at least where I live -- is that the power is off for a
fraction of a second, or hours. There's rarely anything in-between. In general, I'd say that's my seat of the pants impression too, though not always. I also notice they'll often come in clusters. Yes. The glitches are rarely isolated events. Around my area, wind storms often cause sustained outages in areas where the lines are above ground. |
#17
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Observations on a UPS - follow up to a previous post
But be aware that in general, these cheap 'power' meters are expecting 'traditional' sine-draw loads. I have seen wildly inaccurate standby figures being given for equipment, by eco-campaigners that have been let loose with one. A lot of modern equipment that makes use of switch mode power supplies, handles standby mode by brief bursts of full draw operation. This can confuse a simple power calculating algorithm that's expecting continuous draw. Also, the draw by many cheapo switchers is very asymmetric and 'dirty', and may also not produce a true reading. I wouldn't connect a UPS to a fridge. These things are notorious for pulling a short-term startup current of tens of amps, as they get the compressor turning over. The UPS would probably fall over before being able to supply this, and might, as someone else suggested, even sustain damage. Arfa I have a "Kill-A-Watt" and it appears to display true RMS for voltage and current readings. The voltage reading for a modified sine wave from a standard UPS displays the actual RMS voltage. I do not know what crest factor it can handle but displays power factors of considerably less than unity for most consumer electronics with DC rectifiers off of the line voltage. It is a very nice unit for the price. David |
#18
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Observations on a UPS - follow up to a previous post
"David" wrote in message et... But be aware that in general, these cheap 'power' meters are expecting 'traditional' sine-draw loads. I have seen wildly inaccurate standby figures being given for equipment, by eco-campaigners that have been let loose with one. A lot of modern equipment that makes use of switch mode power supplies, handles standby mode by brief bursts of full draw operation. This can confuse a simple power calculating algorithm that's expecting continuous draw. Also, the draw by many cheapo switchers is very asymmetric and 'dirty', and may also not produce a true reading. I wouldn't connect a UPS to a fridge. These things are notorious for pulling a short-term startup current of tens of amps, as they get the compressor turning over. The UPS would probably fall over before being able to supply this, and might, as someone else suggested, even sustain damage. Arfa I have a "Kill-A-Watt" and it appears to display true RMS for voltage and current readings. The voltage reading for a modified sine wave from a standard UPS displays the actual RMS voltage. I do not know what crest factor it can handle but displays power factors of considerably less than unity for most consumer electronics with DC rectifiers off of the line voltage. It is a very nice unit for the price. David But that's my point. You can't have a 'true' sine-based RMS figure for power consumers that draw a pulsed current. Just because it is a sine wave that's *available*, it doesn't mean that the load will draw anything like a sinusoidal current, from it. The only items that will are those that are totally 'passive' in nature, such as light bulbs. Even power supplies that are transformer based, are likely to draw current in pulses from the available sinusoidal supply, and switch mode power supplies, on which most modern consumer electronics are based, most certainly won't draw a sinusoidal current from the supply. Arfa |
#19
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Observations on a UPS - follow up to a previous post
Doc wrote:
On Aug 12, 10:24 pm, "James Sweet" wrote: A test to find out how long it will actually run the computer sounds like a good idea. That's a good way to kill the battery, these things tend to really punish batteries, after a few complete cycles they're often pretty well toast. You should be fine to try it for a bit, say 5 minutes without issues. Seems I've heard an occasional complete drain-down and recharge will extend the life of a rechargeable battery, that being constantly partially discharged and recharged is what shortens their life. Not so? Does it depend what kind of rechargeable it is? It does not extend the life. Back in the seventies when NiCd packs had memory effect, folks were recommending deep discharge. But today, you are more likely to wreck a NiCd pack by reverse-charging a cell that way. The cheap UPSes use gel-cells, which are gelled-electrolyte lead-acid batteries. They are better at surviving deep discharge than NiCd packs, but they still don't like it. Consequently, most equipment that uses them will shut off when the battery voltage drops too low, to prevent damage. Electronics are cheaper than batteries. Bigger UPS units use liquid-electrolyte cells so you can check the battery condition with a hydrometer periodically, and they also have a pulsed charging system that prevents sulfates from building up on the plates. The Wal-Mart cheapies probably do not. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#20
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Observations on a UPS - follow up to a previous post
"Arfa Daily" wrote in message ... "David" wrote in message et... But be aware that in general, these cheap 'power' meters are expecting 'traditional' sine-draw loads. I have seen wildly inaccurate standby figures being given for equipment, by eco-campaigners that have been let loose with one. A lot of modern equipment that makes use of switch mode power supplies, handles standby mode by brief bursts of full draw operation. This can confuse a simple power calculating algorithm that's expecting continuous draw. Also, the draw by many cheapo switchers is very asymmetric and 'dirty', and may also not produce a true reading. I wouldn't connect a UPS to a fridge. These things are notorious for pulling a short-term startup current of tens of amps, as they get the compressor turning over. The UPS would probably fall over before being able to supply this, and might, as someone else suggested, even sustain damage. Arfa I have a "Kill-A-Watt" and it appears to display true RMS for voltage and current readings. The voltage reading for a modified sine wave from a standard UPS displays the actual RMS voltage. I do not know what crest factor it can handle but displays power factors of considerably less than unity for most consumer electronics with DC rectifiers off of the line voltage. It is a very nice unit for the price. David But that's my point. You can't have a 'true' sine-based RMS figure for power consumers that draw a pulsed current. Just because it is a sine wave that's *available*, it doesn't mean that the load will draw anything like a sinusoidal current, from it. The only items that will are those that are totally 'passive' in nature, such as light bulbs. Even power supplies that are transformer based, are likely to draw current in pulses from the available sinusoidal supply, and switch mode power supplies, on which most modern consumer electronics are based, most certainly won't draw a sinusoidal current from the supply. Arfa Arfa, I know that the current draw on these things is anything but sinusoidal. My point was that the "Kill-A-Watt" seems to actually compute the RMS value for that complex current waveform as well as non-sinusoidal voltage waveforms. David |
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