Ups Battery Question

[Tywais]

Just a small comment. The main problem with pseudo, modified or stepped sinewave are the harmonics in it. Neither motors nor transformers are very happy with these and can cause excessive heating. Also microwave ovens are problematic but doubt anyone running them off a UPS. And CF (compact fluorescent) lamps with electronic ballasts can be problems and emit RF noise.

As stated, the complexities between the different UPS mode types and associated connected devices is not straight forward or obvious. I've designed inverters before for use with our fuel cell systems and dug into this pretty deeply to determine which mode type and what 220VAC devices I could safely add to the fuel cell/inverter system.

[seedy]

My thanks to Tywais and BangkokImages for taking the time to reply - in depth - to this thread.

My Harmon Kardon Citation 16 power amp does not like modified sine wave - very noisy.

I will now add a pure sine wave inverter to my 'Must have in LOS' list.

Take care.

[thaimite]

Whilst the above theory is correct and true sine waves may be needed for some equipment such as audio amplifiers etc where high frequency electonic noise would cause a problem, I would dispute the need for true sine wave converters with current computer equipment especially PC's, LCD monitors printers and modem/routers.

a. LCD monitors, printers, and modem/routers often run off simple adapters which are not switched mode power supplies. Besides, trusting the quality (generally crappy on consumer level electronics) of switched mode power supplies is problematic at best.

b. None of this is simple, trying to make it so requires generalizing and I wouldn't recommend generalizing when it come to protecting expensive equipment.

c. To most consumers ANY UPS device will appear very heavy as they contain heavy gel cells and more. Don't assume a pure sine wave from any UPS, instead confirm a true sine wave listed in the specifications. A true sign wave UPS is an important feature, it will be listed if it is one. Omission of this specification should raise a flag.

d. When you understand how the electronics work many electronic items will come to mind when it comes to timing. This reference might be helpful. Or scroll down here to where it says "Do I need a pure sine wave", another source, even Ehow lists the same examples of timing devices and which equipment you might want to avoid on anything other than a pure sine wave inverter.

It isn't my wish to argue this or debate theory, but more to encourage those without the electronics background to follow the UPS manufacturers recommendations on what should be powered by their specific UPS devices and even to be skeptical if they see something listed which might be a mistake. It's important to keep in mind that UPS's come in several flavors, modified sine waves and pure sine waves, so don't lump them all together.

I too don't wish to enter in to a lengthy debate, but wish to make a few points.

1st this is a computer forum, so I am assuming most people will use a UPS to power computers where I restate my case that I believe a pure sign wave is overkill for computers and monitors because of the extensive use of switch mode power supplies in these devices.

Certainly motors and equipment with big transformers do not like cheap inverters, and an expensive high quality amp such as a Harmon Kardon should never be powered by anything but the best pure sine wave inverter.

Some of the claims made in the link you sent are definitely wrong, I doubt you will find many digital clocks that use the mains as a reference frequency. This was the case 30 years ago, but not now. They get their reference frequency by other means just like a digital watch.

Having said all that, if you are happy to pay the extra for a pure sign wave device and feel happier then their is no disadvantage in doing so, and if in doubt seek advice from the manufacturer.

Also remember that the power at your hose may not be as clean and pure s you think due to many factors such as CFR lamps and even ordinary fluorescents. I saw a case many years ago where a large pumping station caused interference to the neighbourhood due to its extensive use of large inverters to control th speed of its multiple 500HP pumps.. Fortunately technology has moved on and such things are rare.

Edited December 14, 2011 by astral
No need to quote the entire post. Just pick out the relevant points, please - Astral

[astral]

I am pretty sure my setup does not produce a pure sine wave,

but like Naam I have not experienced any problems as a result.

As stated many electronic units use switching power supplies, TV's and router/modems included, and sometimes they are a serious source of RFI (radio frequency interference) especially for radio amateurs.

[BangkokImages]

I am pretty sure my setup does not produce a pure sine wave,

but like Naam I have not experienced any problems as a result.

As stated many electronic units use switching power supplies, TV's and router/modems included, and sometimes they are a serious source of RFI (radio frequency interference) especially for radio amateurs.

a. I'm glad you haven't noticed problems. But keep in mind, bad power is like a silent killer to electronics. Sometimes you have immediate and obvious problems, sometimes it just removes years off the life of a device.

b. Switching power supplies are often not built nor do they perform as advertised. Most are just plain cheap pieces of junk that barely get the job done. Power supply failure is right up there in the top three failure items and they really shouldn't be. It's easy to build good power supplies, but they do cost more to manufacture. I would never ever ever power a tv I cared about with a modified sine wave UPS. Ask any tv repairman. Any device, usually routers, modems, newer LED backlit monitors, etc, which are powered by a simple adapter.. is probably not a switching power supply. Most are cheap barely adequate power supplies. This is a major area manufacturers cut corners. This probably sounds strange but will make perfect since to any electronics person, but at times when I'm between a few different pieces of gear to buy.. I'll check the heft of the power adapter/supply/device. The better units are run off quality heavier transformers with bigger heavier capacitors.

c. You're right about that. My knowledge (now severely outdated I'm sure) with electronics started in the military with a solid two years of electronics training (8-10 hours a day) which often powered transmitters and other equipment you wanted to remain noise free, and continues to this day as an Extra Class Ham, The noise induced by cheap or faulty power supplies is legendary.

[BangkokImages]

I too don't wish to enter in to a lengthy debate, but wish to make a few points.

1st this is a computer forum, so I am assuming most people will use a UPS to power computers where I restate my case that I believe a pure sign wave is overkill for computers and monitors because of the extensive use of switch mode power supplies in these devices.

Certainly motors and equipment with big transformers do not like cheap inverters, and an expensive high quality amp such as a Harmon Kardon should never be powered by anything but the best pure sine wave inverter.

Some of the claims made in the link you sent are definitely wrong, I doubt you will find many digital clocks that use the mains as a reference frequency. This was the case 30 years ago, but not now. They get their reference frequency by other means just like a digital watch.

Having said all that, if you are happy to pay the extra for a pure sign wave device and feel happier then their is no disadvantage in doing so, and if in doubt seek advice from the manufacturer.

Also remember that the power at your hose may not be as clean and pure s you think due to many factors such as CFR lamps and even ordinary fluorescents. I saw a case many years ago where a large pumping station caused interference to the neighbourhood due to its extensive use of large inverters to control th speed of its multiple 500HP pumps.. Fortunately technology has moved on and such things are rare.

a. I thank you for the friendly and informative discussion. I love talking about this stuff as I'm always learning/updating my knowledge which admittedly is dated.

b. True, this is a computer forum and most people buy UPS devices with their computers in mind. But once they have one they often plug other expensive electronics into them thinking it's better to take advantage of their UPS which can be a mistake.

c. You have a lot more faith in switching power supplies than I do. I'll say this, server grade equipment will normally have power supplies (switching) several levels above normal consumer equipment, but every quality server grade UPS you'll find out there outputs a pure sine wave. IT professionals consider it cheap insurance. So do I. A second point, don't assume your power supply (especially adapters) are switching power supplies. Even if they are, they're usually the cheapest possible.

d. I totally agree, household power, especially in Thailand, can be extremely dirty for a variety of reasons. Enough so that it will give even great power supplies fits. When I test/review computer power supplies I always pull out the old Tektronix O'scope and measure ripple, and more than a few times in Thailand I've found the household power so dirty that even a great power supply like the old PC Power and Cooling or the newer Seasonics were exhibiting significant ripple. Ironically, plugging the supply into a pure sine wave Inverter or UPS cleaned it up enough to reduce or eliminate the ripple. As a ham it's common for your local club to have a few guys knowledgeable about this subject who come out to other hams homes and track down sources of noise or bad power. At first it's surprising what you find, but after a while you get used to it.

And once again, if anyone runs across the outlet where they sell refurbished APC UPS's inside Thailand please share. The discounts are often deep enough to make buying a server class UPS less expensive than a new consumer class.

[InterestedObserver]

Ironically, plugging the supply into a pure sine wave Inverter or UPS cleaned it up enough to reduce or eliminate the ripple.

Certainly. As with most things UPS related, unless on mains bypass, you are usually isolated by a DC-AC inverter stage. Oops, there goes that pesky electrical noise garbage!

[thaimite]

I too don't wish to enter in to a lengthy debate, but wish to make a few points.

a. I thank you for the friendly and informative discussion. I love talking about this stuff as I'm always learning/updating my knowledge which admittedly is dated.

b. True, this is a computer forum and most people buy UPS devices with their computers in mind. But once they have one they often plug other expensive electronics into them thinking it's better to take advantage of their UPS which can be a mistake.

Thanks to you too for the informative discussion. It would have been even nicer over a cold beer or two, but alas I am working away as usual.

I too started with high power maritime RF systems, when "tubes" or "Valves" to us Brits were still in service although not used much except for high power equipment. However since then I have done a lot in industrial control and now airport IT systems but it is getting harder and harder to keep my knowledge up to date.

I think if you look around you will be surprised as to how common switch mode power supplies are (I was) Even you [hone charger is probably switched mode, and the use of microprocessors has made it much easier for cheap UPS units to get a better waveform than even 10 years ago.

Edited December 14, 2011 by astral
No need to quote the entire post. Just pick out the relevant points, please - Astral

[Naam]

I totally agree, household power, especially in Thailand, can be extremely dirty for a variety of reasons. Enough so that it will give even great power supplies fits. When I test/review computer power supplies I always pull out the old Tektronix O'scope and measure ripple, and more than a few times in Thailand I've found the household power so dirty that even a great power supply like the old PC Power and Cooling or the newer Seasonics were exhibiting significant ripple.

Lawd (and BangkokImages) please have mercy! what is "dirty power" and who or what is a "ripple"?

just googled ripple, read and feel like my gardener when i try to explain some of my special knowledge in quantum physics.

"The most common meaning of ripple in electrical science is the small unwanted residual periodic variation of the direct current (dc) output of a power supply which has been derived from an alternating current (ac) source. This ripple is due to incomplete suppression of the alternating waveform within the power supply."

Edited December 15, 2011 by Naam

[BB1950]

Lawd (and BangkokImages) please have mercy! what is "dirty power" and who or what is a "ripple"?

just googled ripple, read and feel like my gardener when i try to explain some of my special knowledge in quantum physics.

"The most common meaning of ripple in electrical science is the small unwanted residual periodic variation of the direct current (dc) output of a power supply which has been derived from an alternating current (ac) source. This ripple is due to incomplete suppression of the alternating waveform within the power supply."

Naam in very simple terms:

Dirty power = Power that is not clean or pure (i.e. direct voltage that is not constant or alternating voltage that is not a pure sine wave).

Ripple = Small periodic, usually undesirable, variations in electrical voltage superposed on a direct voltage or on an alternating voltage of lower frequency.

[Naam]

Naam in very simple terms:

Dirty power = Power that is not clean or pure (i.e. direct voltage that is not constant or alternating voltage that is not a pure sine wave).

Ripple = Small periodic, usually undesirable, variations in electrical voltage superposed on a direct voltage or on an alternating voltage of lower frequency.

thanks for the explanation BB. i know that we have voltage fluctuations and that especially to the downside which cost me initially quite some money and sweat to replace burned pump and aircon relays. problem is solved since i had some gear built that switches off any phase when voltage varies ±5% from a median of 230V. i can also adjust that variance stepless up to ±20% but stay on the safe side.

however, besides the relays i never had any problems with electronic items such as computers, TV, audio and the like. unfortunately light bulbs seem to be a consumer item in Thailand, whether conventional or power saving. my average = 48 hours / 1 bulb

[InterestedObserver]

unfortunately light bulbs seem to be a consumer item in Thailand, whether conventional or power saving. my average = 48 hours / 1 bulb

Light bulbs, especially energy saving or CFL, that only last 48 hours is a good indication that something is not normal with the electrical system.

[BangkokImages]

Ironically, plugging the supply into a pure sine wave Inverter or UPS cleaned it up enough to reduce or eliminate the ripple.

Certainly. As with most things UPS related, unless on mains bypass, you are usually isolated by a DC-AC inverter stage. Oops, there goes that pesky electrical noise garbage!

Yes, of course.

Edited to remove stupidity.

Edited December 16, 2011 by BangkokImages

[BangkokImages]

I too don't wish to enter in to a lengthy debate, but wish to make a few points.

a. I thank you for the friendly and informative discussion. I love talking about this stuff as I'm always learning/updating my knowledge which admittedly is dated.

b. True, this is a computer forum and most people buy UPS devices with their computers in mind. But once they have one they often plug other expensive electronics into them thinking it's better to take advantage of their UPS which can be a mistake.

Thanks to you too for the informative discussion. It would have been even nicer over a cold beer or two, but alas I am working away as usual.

I too started with high power maritime RF systems, when "tubes" or "Valves" to us Brits were still in service although not used much except for high power equipment. However since then I have done a lot in industrial control and now airport IT systems but it is getting harder and harder to keep my knowledge up to date.

I think if you look around you will be surprised as to how common switch mode power supplies are (I was) Even you [hone charger is probably switched mode, and the use of microprocessors has made it much easier for cheap UPS units to get a better waveform than even 10 years ago.

No doubt..

This reminds me of when I first got into this.. we studied tubes (loved the walk in variety), then bi-mags, then solid state modules, and finally IC chips.. I entered in a time when all the technologies were in use, either at the end of their technology cycles or just beginning. It's tough to keep up with this stuff if you don't keep up on a daily basis, but I will take you up on the switched supplies and put some effort into increasing my knowledge.

[BangkokImages]

unfortunately light bulbs seem to be a consumer item in Thailand, whether conventional or power saving. my average = 48 hours / 1 bulb

Light bulbs, especially energy saving or CFL, that only last 48 hours is a good indication that something is not normal with the electrical system.

+1

[BB1950]

unfortunately light bulbs seem to be a consumer item in Thailand, whether conventional or power saving. my average = 48 hours / 1 bulb

Light bulbs, especially energy saving or CFL, that only last 48 hours is a good indication that something is not normal with the electrical system.

+1

+2

[thaimite]

This reminds me of when I first got into this.. we studied tubes (loved the walk in variety), then bi-mags, then solid state modules, and finally IC chips.. I entered in a time when all the technologies were in use, either at the end of their technology cycles or just beginning. It's tough to keep up with this stuff if you don't keep up on a daily basis, but I will take you up on the switched supplies and put some effort into increasing my knowledge.

Sounds like we come from a similar vintage.

On my current project, all servers and network equipment in the data centres are a in redundant configuration, each piece of equipment hs dual switched node power supplies fed from redundant UPS units which are supposed to keep the systems runnmng until the generators start. All the other airport systems operate from a few centralised UPS units. (redunant of course)

One technology that intrigues me is Flywheel UPS. I have never seen one but maybe oneday

And my apologies to everyone for talking this thread off course.

Edited December 16, 2011 by astral
No need to quote the entire post. Just pick out the relevant points, please - Astral

[Naam]

unfortunately light bulbs seem to be a consumer item in Thailand, whether conventional or power saving. my average = 48 hours / 1 bulb

Light bulbs, especially energy saving or CFL, that only last 48 hours is a good indication that something is not normal with the electrical system.

obviously a misunderstanding because of my german english. i meant every 48 hours one of the 80 or 90 bulbs in or around my house conks off and has to be replaced. but based on the complaints i read in other threads that seems to be quite normal.

[Naam]

One technology that intrigues me is Flywheel UPS. I have never seen one but maybe oneday

And my apologies to everyone for talking this thread off course.

no need to apologise! there's at least one party that is interested and was involved in flywheel applications although in half-àssed and much less sophisticated ones. many rainy seasons ago we used flywheels flanged to back-up generators to bring them up in a fraction of a second to required RPMs in case of main power failure.

[BangkokImages]

This reminds me of when I first got into this.. we studied tubes (loved the walk in variety), then bi-mags, then solid state modules, and finally IC chips.. I entered in a time when all the technologies were in use, either at the end of their technology cycles or just beginning. It's tough to keep up with this stuff if you don't keep up on a daily basis, but I will take you up on the switched supplies and put some effort into increasing my knowledge.

Sounds like we come from a similar vintage.

On my current project, all servers and network equipment in the data centres are a in redundant configuration, each piece of equipment hs dual switched node power supplies fed from redundant UPS units which are supposed to keep the systems runnmng until the generators start. All the other airport systems operate from a few centralised UPS units. (redunant of course)

One technology that intrigues me is Flywheel UPS. I have never seen one but maybe oneday

And my apologies to everyone for talking this thread off course.

Ah, but they were good times..

Back in the day.. when we were responsible for keeping small intelligence stations running (NSGA's and CRITICOMS) the bottom deck would be one large UPS center. Antiquated by todays standards I'm sure, but they worked something like this: We had rows and rows of wet cell batteries which weighed several hundred pounds each, a typical small station would have a room roughly 40x50 meters full of these. Larger stations of course had more of everything. These were charged through large wet transformers that had to have their oil changed at regular intervals. Dual large (twice as tall as a man) diesel generators were always on standby in the event shore power went down. They would be 'test' started twice a day and ran up for 15 minutes each after normal operating temperature was reached. Automatic switching would bring them on-line after their output stabilized at roughly 5-10 minutes after the power outage. One generator was designed to run the entire load, but two was redundant in the event one failed or couldn't stabilize which was sometimes an issue. A SEABEE would be on duty continuously (24/7/365) and would work their entire shifts checking battery levels, checking/changing generator oils/filters/etc, rotating transformers, and whatnot.. It was always a site to watch them crane in a replacement generator or transformer.

Power panels were marked red and mission essential equipment would receive their power from these panels, which in the SCIF's themselves would including lighting and heating/air. The rest of the building would run off shore power but the generators would power them once up.

A typical outage would see admin/shop/regular areas go dark, battle lanterns go on (these required a heck of a lot of maintenance too), while not a blink too place inside the SCIFs as the red panels ran off batteries and not shore power. 5-10 minutes later the lights in the regular areas would blink a few times then stay on.. and a shorter reversal after shore power was available again, though it was protocol to stay on emergency power for at least 30 minutes after it was back on and stabilized.

When an outage occurred we were all called in and had to stand by in the event something went wrong and we had to do emergency shutdowns of mission essential gear. Back then computers and "IT" equipment used a lot more power for what they actually did.

How long ago? You probably know the modern internet runs on a modern variant of the X.25 packet protocol, a ham radio invention btw.. and I was on the team that installed (in three different geographical locations) and brought on line what I think was the worlds first connected stations that exchanged/shared information via X.25. It was code named NETWORKS. The three stations basically were a small internet.

I remember our first hard disk platters (running up tapes was a time consuming process) that resembled extra-large washing machines with a stack of platters on the top, and when the spun up it mimicked a "spin cycle" of a washing machine. 10mb each set of platters if I remember right. Head adjustments were first done by eye with a large pair of needle nosed pliers.

I could go on and on with this stuff.. we were sent to equipment sponsored schools roughly 30% of each year on average. Hewlett Packard, Texas Instruments, and so on and on.. it seemed impossible to keep up.. and this was just the networks/IT side. The crypto side had it's own evolutions and challenges in staying current.

I'm pretty sure a modern mid-grade desktop has more capability than an entire station had back then.. Anyone remember loading programs with punch cards? Or making 'slight' program changes with card punches which you always carried on your key chain? Or being able to read baudette tape with your finger tips?

Vintage... yup..

[BangkokImages]

unfortunately light bulbs seem to be a consumer item in Thailand, whether conventional or power saving. my average = 48 hours / 1 bulb

Light bulbs, especially energy saving or CFL, that only last 48 hours is a good indication that something is not normal with the electrical system.

obviously a misunderstanding because of my german english. i meant every 48 hours one of the 80 or 90 bulbs in or around my house conks off and has to be replaced. but based on the complaints i read in other threads that seems to be quite normal.

Yes, in Thailand where power is generally so dirty this would be normal. Though, I'd suggest if it's happening more on one fixture than another that you test to see which breaker circuit the fixture is on. Often times a Thai "electrician" thinks nothing of wiring a fixture into a circuit without checking to see if it's an air conditioning, refrigerator, or stove top/oven circuit. Any circuit running motors or heavy heating elements/strips will pop bulbs quite often. With older buildings which have been remodeled several times, the electric circuits can be very.. umm.. mingled. When my landlord renovated my 12 year old condo to keep me from moving, he couldn't understand why a complete rewiring was on my list of demands. Until the electrician explained what he found.

[Naam]

Yes, in Thailand where power is generally so dirty this would be normal. Though, I'd suggest if it's happening more on one fixture than another that you test to see which breaker circuit the fixture is on. Often times a Thai "electrician" thinks nothing of wiring a fixture into a circuit without checking to see if it's an air conditioning, refrigerator, or stove top/oven circuit . Any circuit running motors or heavy heating elements/strips will pop bulbs quite often. With older buildings which have been remodeled several times, the electric circuits can be very.. umm.. mingled. When my landlord renovated my 12 year old condo to keep me from moving, he couldn't understand why a complete rewiring was on my list of demands. Until the electrician explained what he found.

that's definitely not the case. all my aircons (there are 19 of them ) as well as all pumps, washer, dryer, cooking range, oven, fridges, water heaters are on individual dedicated circuits and breakers. the same goes for lighting and socket circuits of which a least three dozen individual ones exist. as i was curious i just counted the number of breakers/cicuits and came up with a total of 64 (sixty-four)... equivalent to a dozen Thai homes in the boonies

[BangkokImages]

Yes, in Thailand where power is generally so dirty this would be normal. Though, I'd suggest if it's happening more on one fixture than another that you test to see which breaker circuit the fixture is on. Often times a Thai "electrician" thinks nothing of wiring a fixture into a circuit without checking to see if it's an air conditioning, refrigerator, or stove top/oven circuit . Any circuit running motors or heavy heating elements/strips will pop bulbs quite often. With older buildings which have been remodeled several times, the electric circuits can be very.. umm.. mingled. When my landlord renovated my 12 year old condo to keep me from moving, he couldn't understand why a complete rewiring was on my list of demands. Until the electrician explained what he found.

that's definitely not the case. all my aircons (there are 19 of them ) as well as all pumps, washer, dryer, cooking range, oven, fridges, water heaters are on individual dedicated circuits and breakers. the same goes for lighting and socket circuits of which a least three dozen individual ones exist. as i was curious i just counted the number of breakers/cicuits and came up with a total of 64 (sixty-four)... equivalent to a dozen Thai homes in the boonies

Well dam_n Namm.. you're running your own substation.. Of course all these things are supposed to be on dedicated circuits.. but you do know you're in Thailand right?

[Naam]

Well dam_n Namm.. you're running your own substation.. Of course all these things are supposed to be on dedicated circuits.. but you do know you're in Thailand right?

believe it or not... the Thai electrician who did the wiring of my home knew exactly what i expected. there was no need for me to push him.

[astral]

A single phase supply or three phase?

The latter I guess.

I wonder what your electric bill is each month?

All the same, with all that equipment in your house

you will be creating your own dirt on the supply.

[BKKdreaming]

Just an idea ,

if you have a server UPS , and its hooked up to a good sized truck battery that is charged by a seperate 12v wall charger to keep it topped up ,

if you lose mains power , Will the server UPS run for days as a back-up as long as the truck battery has power ?

Just wondering if the server UPS has a limit on hours run before it fries !

and lets say this is at 35-40C 85-95F outside temp.

Just thinking of a cheap back-up power for the house if the power goes out for a few days ,

I have a 1000 watt Honda generator too

BK

[astral]

Just an idea ,

if you have a server UPS , and its hooked up to a good sized truck battery that is charged by a seperate 12v wall charger to keep it topped up ,

if you lose mains power , Will the server UPS run for days as a back-up as long as the truck battery has power ?

The charger must be able to provide enough power to keep up with the normal server load

AND be able to recharge after a power outage

Just wondering if the server UPS has a limit on hours run before it fries !

and lets say this is at 35-40C 85-95F outside temp.

The UPS must be conservatively configured and have adequate cooling and ventilation,

then it should be able to run as long as the battery has power.

It will struggle once the battery voltage starts to drop............

[thaimite]

Just an idea ,

if you have a server UPS , and its hooked up to a good sized truck battery that is charged by a seperate 12v wall charger to keep it topped up ,

if you lose mains power , Will the server UPS run for days as a back-up as long as the truck battery has power ?

The charger must be able to provide enough power to keep up with the normal server load

AND be able to recharge after a power outage

Just wondering if the server UPS has a limit on hours run before it fries !

and lets say this is at 35-40C 85-95F outside temp.

The UPS must be conservatively configured and have adequate cooling and ventilation,

then it should be able to run as long as the battery has power.

It will struggle once the battery voltage starts to drop............

A good UPS should shut down once the battery voltage drops below a usable level otherwise harm may be done to your computer or the UPS.

It it was my set up I would rather have the additional battery and charging separated., and then switched in once the power fails otherwise there maybe a chance of the 2 charging circuits conflicting. It maybe possible to come up with some diode arrangement for this, but I would prefer a relay that parallels the batteries on mains failure.

Edited December 17, 2011 by thaimite

[BKKdreaming]

Thanks for your ideas,

I really would not we using it as a server UPS that had to keep a computer active 24/7 ,

I would more like to have an electrical back-up in case the mains power went down so I could still use my computer/ monitor and a few other electrical items till the power came back on.

But say its off for a couple days , then the truck battery would help keep me going.

Maybe I would be better off with a high priced 12v to mains converter but used server UPS I think are better quality and full sine wave.

Just my thoughts....often wrong !

BK

[BangkokImages]

Thanks for your ideas,

I really would not we using it as a server UPS that had to keep a computer active 24/7 ,

I would more like to have an electrical back-up in case the mains power went down so I could still use my computer/ monitor and a few other electrical items till the power came back on.

But say its off for a couple days , then the truck battery would help keep me going.

Maybe I would be better off with a high priced 12v to mains converter but used server UPS I think are better quality and full sine wave.

Just my thoughts....often wrong !

BK

A server class UPS of course comes with a larger battery with a lot more capacity, but not what you're talking. Electronic devices often come with an advertised "duty cycle" listed in the specs. What this means is that if you're using it within specs, it will run say 50% of the time with a 50% rest break if the duty cycle is 50%, or it might be 100%. Or it might be 100% at a 50% load and 50% at a 100% load. But the reality is, UPS devices duty cycles are designed in line with the capacity of their internal batteries. Some might run a lot longer if properly cooled, but if you're exceeding that internal battery by much you probably want to look for a different alternative.

In your case.. why not look for a high quality generator? A small 1000 watt generator will keep a few lights and your computer stuff going as long as you have fuel. I stress "high quality" because generators vary in clean/dirty output quite a bit. So before plugging your UPS into a generator make sure it's a quality generator.

A more expensive alternative would be a bank of batteries and a quality inverter of the type used with alternative energy setups like solar power. You can keep the batteries charged via regular power and not use the solar panels for instance. Your capacity would then only be limited by the capacity if your batteries and inverters. Many modern homes have such emergency power sources built in and backed up by generators. There are stores that specialize in this sort of equipment. Of course it can be expensive, but you could probably rig something up for a computer station for a reasonable price and still keep the quality high by using equipment meant for the job. For sure you don't want a big wet cell battery in your home. You need proper venting and ventilation and rated fire extinguishers for sure.

It would make for a fun project as well. In this part of the world Chinese diesel generators aren't that expensive, but I'd much rather have a quality Japanese built unit.