calculation for UPS

[tineng]

Hi anyone knows how to calcuate how long a pump will run on UPS????

for example a 11w tunze pump on a 0.5kva UPS????

[roidan]

http://www.apc.com/products/runtime_for_ex...m?upsfamily=165

say under 230V,

drawing 50W, around 500VA can last over an hour...

so 11W should pass 2 hours with ease...but not too sure what exact runtime.

[tineng]

http://www.apc.com/products/runtime_for_ex...m?upsfamily=165

say under 230V,

drawing 50W, around 500VA can last over an hour...

so 11W should pass 2 hours with ease...but not too sure what exact runtime.

still don't get it...if 500va can power 50w for 1 hour....why 11w only 2??? i thought using be 4 hours????

also have one have any idea if i cascade 2 0.5kva UPS together does it means i have twice the duration????

reason I'm asking is the the 0.5kva are going quite cheap now....

[roidan]

i never say only 2 hours mah...

i say should pass 2 hours with ease....that' why i also say actual runtime i also won't know unless the real application is done and timed

as for connecting in series...not too sure if that is recommended.

go email the tech support of the UPS brand to ask for runtime and the effect of using a few lor...

[tineng]

yeah...guess we never know until we try....anyway...was exploring the site and found that by comparing products there is a functions for you to key in your watt to get the run time.....for a 500va UPS i got 4hours 21 min....

this thing very confusing to me....a 500va UPS cost S$65 but a 1000va UPS cost S$395????....now thinking if i should cascade 3 of them (if possible ) to give me a 12hr runtime...so can wait till i go home from work....or to figure out a way to pull a super long phone line to my tank and call me when there is a power out.....

[roidan]

sure got reason one lah..

if not the $395 can buy 6 x 500VA become 3000VA UPS liao ah...

[tineng]

wonder if any of these power engineer types cares to enlighten us.....anyway, company doing a bulk order....maybe i place a order for 2 peice....1 to power the tank and place near the phone point to call me ...then don't have to pull a ugly phone line already....

[roidan]

just before u buy the one for your tank....

is this UPS pure-sine wave version?

because alot of cheap computer UPS are stepped/modified sine wave versions that will not work properly with your stream....

our streams/pumps need pure/true sine wave UPS to work properly.

if u are talking about APC brand...it will be their SMART-UPS series.

[weileong]

The UPS still runs on lead acid cell. The Ah (amps-hr) rating is rated on a certain low amps (example 500mA).

If now you draw a current of 1Amps then Ah rating will be lower than when you are drawing 500mA.

For example for a 150Ah deep cycle battery (rated at 5amps), you draw 5amps and it will supply you current for 30hrs.

Now you draw 25amps it probably can supply only abt 3 hrs.

For the higher rated UPS they are designed to handle bigger current, uses larger battery so a double increase in rating usually means a much higher increased in battery size and circuitry and also more $$$$

[tineng]

just before u buy the one for your tank....

is this UPS pure-sine wave version?

because alot of cheap computer UPS are stepped/modified sine wave versions that will not work properly with your stream....

our streams/pumps need pure/true sine wave UPS to work properly.

if u are talking about APC brand...it will be their SMART-UPS series.

thanks bro...will check it out....the S$65 bucks ones are from APC but i think not pure sine wave..... guess will be quite useless to buy them for tank use.....anyway, will try to sneak one out of office to try....

[tineng]

The UPS still runs on lead acid cell. The Ah (amps-hr) rating is rated on a certain low amps (example 500mA).

If now you draw a current of 1Amps then Ah rating will be lower than when you are drawing 500mA.

For example for a 150Ah deep cycle battery (rated at 5amps), you draw 5amps and it will supply you current for 30hrs.

Now you draw 25amps it probably can supply only abt 3 hrs.

For the higher rated UPS they are designed to handle bigger current, uses larger battery so a double increase in rating usually means a much higher increased in battery size and circuitry and also more $$$$

still confuse....but make sense in a way....thanks bro for the info...

[patrick123]

Tineng,

If got bulk order, can help me buy or not? I will get it if it is pure-sine wave one. May be for non pure-sine wave can use a normal pump...if spoil already just throw away.

Please pm me.

BTW, is there such feature that the APC UPS will call you when there is a power outage? This will be a very handy feature in my opinion. Worth getting it since it only cost S$65. So eventhough the battery will not last, but at least it will alert you and you can take a half day leave to go home. It is only 1/2 hour away.

[AlfaRomeo]

You cant daisy chain UPSes. Sumthing to do with modifed sinewave etc etc. It will spoilt the UPSes down the chain. I dunt really know exctly why but when I design datacentres, UPSes are all in parallel in-line and not in series. Partly due to the difference power phases that we have.

[kareen]

You cant daisy chain UPSes. Sumthing to do with modifed sinewave etc etc. It will spoilt the UPSes down the chain. I dunt really know exctly why but when I design datacentres, UPSes are all in parallel in-line and not in series. Partly due to the difference power phases that we have.

Could this be the reason?

For eg. 2 1.5V battery in series, the voltage drop across it is 3V. While 2 1.5V battery in parallel is 1.5V but can supply more current.......

[AlfaRomeo]

Could this be the reason?

For eg. 2 1.5V battery in series, the voltage drop across it is 3V. While 2 1.5V battery in parallel is 1.5V but can supply more current.......

Nope. UPSes dunt increment the voltage provided even when linked in Series. It has sumthing to do with the charging and discharging signaling on the separate UPSes. You can only link UPS in series if the UPS can communicate with each other thru a comms channel. Even possible, its not recommended.

[kareen]

then can connect it in parallel?

[AlfaRomeo]

Yes. Connecting in parallel is advisable with each UPS supplying a different 'circuit' so to speak. Also gotta take note the a stepped sinewave will damage pumps in the long run so you need the true sinewave versions... which are not cheap. Stepped sinewaves are meant for devices equipped with its own filtering/regulating power supplies. PCs etc etc would be suitable for these 'lower-end' UPSes.

[tineng]

bro patrick123, you be disappointed at the price of the bulk purchase as its the same as some shop in sim lim selling....reason i'm considering this purchase is because they deliver to my office and i wouldn't need to make an extra trip there.......

bro Alfa...thanks for the advise, guess i'll drop the idea of a cheapo UPS and hunt around for some fire sales for good UPS....anyway, 1 more question....does the UPS kicks in only when there is a power failure and during normal operating condition its just a by-pass without affecting the sinewave, or does it use its own stepped sinewave as long as its in operation????

[AlfaRomeo]

Its output is a continuous stepped sinewave or true sinewave irregardless of if its on mains or battery. hth

[Marineman]

I got an UPS 500VA backed by a car battery 70AH, can run my 80W pump for 7 hours, cost about S$450. I am not a technical guy so cannot really explain the calculation, it's a lot cheaper than getting a high pwered UPS which can cost a fortune.

[surfedelic]

How about if get use a Car batt and a DC-AC converter .... does it works ? If it works then get a Solar panel .... put in my balcony charge up the Batt during normal days

[tineng]

I got an UPS 500VA backed by a car battery 70AH, can run my 80W pump for 7 hours, cost about S$450. I am not a technical guy so cannot really explain the calculation, it's a lot cheaper than getting a high pwered UPS which can cost a fortune.

how is that done??? a UPS backed by a car battery.....

[wedgee]

Please note that a car battery is a quick-charge type of battery that also supplies a large amount of voltage in a short amount of time, so if u havent tried out the real thing yet, please do not assume the calculation will be correct.

If in the event of a power failure, the surge of power from the car battery may well damage the UPS, as the UPS has a fixed AH rating, and a lowest voltage that it can discharge the battery to...Using a non-complying battery may damage your UPS or if u are in luck, it may just burn out too fast...

After dat, your UPS may not be able to charge up the battery again, as the charging current is supposedly much higher than a normal UPS battery...

As for the Series and parallel question - using 2 UPS in series will supposedly provide u with a longer runtime, but give u a larger electricity bill, as dual-conversion UPSes run on average 80-90% efficiency, so if u chain 2 of them up, u waste about less than half of your input power as opposed to the output, thereby increasing your bill over the long run...

In parallel, u are better protected against breakdowns of any of the 2 UPS, but in order to run parallel, u need some switches and equipment (not very cheap) to ensure the supply is seamless when power failure occurs and one UPS runs out or in the event that one UPS fails during a normal day...

[Rocky99]

the car battery idea is great. hook up a few more can back up my MHs.

correct me if i'm wrong. i thought car battery is usually 12V.

[narkosis]

the car battery idea is great. hook up a few more can back up my MHs.

correct me if i'm wrong. i thought car battery is usually 12V.

Bro,

They are. Power backup units like the one Marineman is using come with a built-in 12V charger, and an inverter that converts DC to AC, and then is amplified back up to 220/240V, with our local frequency of 50Hz. This is the main reason why they're pretty expensive - it's not as easy as what most people think.

And with models like this, you can connect multiple 12V car batteries in parallel, thus increasing the Ah rating, and thus the power-up period during a blackout. Of cos, the more batteries you have, the longer it will take all of them to charge up.