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How to calculate UPS battery backup | Backup HowTo
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How to calculate UPS battery backup March 4, 2009 - 11:55 |
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It is nearly impossible to know when the next power outage will occur and frankly, they can be rather damaging unless you have the tendency to save your work every 2 minutes. I remember I have been working on this Photoshop file for nearly two hours, and a power outage came and erased everything I worked on – the next day I went to the market and bought an UPS. Now, before I bore you with useless stories let us see what you can find within this article: The answer to the popular question “how to calculate ups battery back-up” What is an UPS (with friendly details) What types of UPS you can find on the market
Introduction to the UPS battery back up UPS (Uninterruptible Power Supply) systems have been built to compensate for those power outages and to help you save your system and your work. You might have found out by now that those sudden changes in voltages can affect your computer – it can damage your power system along with your main board and CPU. Aside from this, it can produce light damage to your hard drives and other devices you have in your computer. The bottom line is – power outages are harmful for both your work and your PC. The thing is, UPS’ have become quite useful especially nowadays when they can have up to one hour battery back-up which gives you enough time to complete your work and shut down the computer safely. However, how does a UPS work? Simple, when your power line distributes power within normal parameters, the UPS stores power, therefore whenever a power outage occurs UPSes act like a battery (similar to the back-up battery existing in laptops, only larger and based on a different principle). [inline:1] Any UPS system is placed between your equipment and the power socket. When electricity flows from the socket to the UPS and then to the computer, the battery is continuously checking power levels, and collecting power at the same time. When the electricity flow is not within normal parameters anymore, the UPS will start compensating for the lack of power by connecting the batteries. Once the power flow has been restored, the UPS will start recharging its batteries again. Owning an UPS, battery back up will not only protect you from power outages, but also from changes in the power flow (lower voltage may damage your components too).
Types of UPS battery back-up The market is full of UPS battery back-up systems and some of them have different purposes. Here are the two most popular types you can find on the market at any time: Offline UPS – Offline UPS battery back-up systems work similar to laptop batteries. Once the power source is removed, they kick in and supply the needed amount of power, and once the power outage is removed, the UPS goes back to recharging its batteries. The only inconvenience here is the fact that when power is restored, the UPS temporarily closes the transfer of power between the computer and the source thus making it an unreliable choice in many cases. Online UPS – This is one of the most reliable types of UPS battery back-up systems since they provide electricity at any time, without any closing down of power transfers (similar to the offline UPS). Basically, an online UPS will not only protect your computer for power outages, but also from voltage irregularities.
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outages, but also from voltage irregularities.
How to calculate UPS battery backup | Backup HowTo
How to calculate ups battery backup When I first asked this question myself, a friend of mine kindly sent me to the manual (a joke, obviously). In the meantime, I found out that calculating ups batter back up is not such a big deal as I might have thought in the first place. In order to make everything as clear as I can, I will use a small example. Let us assume the following ideas: Inverter efficiency of UPS battery is 90% (the norm is somewhere between 90% and 98%) Battery end point voltage 1.67 (usually specified on the UPS itself, or in its manual) Environmental temperature 77F
Assuming that we know the following things about our UPS : one string of batteries, 30 each, UPS rating 40kW and 6 cells per unit, we can break down the calculations in three steps: 1.) Actual battery load for 40kW
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40kW … 90% efficiency means an actual 44.4kW load (you can calculate this by dividing the rating of the UPS by inverter efficiency – 40/0.9 = 44.4kW)
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2.) Watts per Battery 44.4kw (previously calculated) will be divided by the number of batteries we have available, and the result will lead to 1481 watts per battery. (you can calculate this using the equation: 44.4Kw/30 = 1481W) 3.) Watts per each Cell Giving the necessary data we will deduct that each cell needs 247W. (calculate this using the equation: 1481W / 6 (the number of cells per unit) = 247 watts per each cell) Now we can easily estimate the run-time of your UPS battery back up system. Giving the fact that we know that each batter has about 247W per each cell, and we have a battery end point voltage of 1.67V your run time should be somewhere between 45 minutes and 60 minutes. Tags: UPS Articles: Others Bookmark/Search this post with 1
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Comments Permalink Submitted by Kamal Ahmad (not verified) on August 20, 2009 - 00:00.
ups backup time
Can you help me how you calculate the back up time from 45 to 60 miutes can you provide me with the equation Log in or register to post comments Permalink Submitted by jignesh (not verified) on August 25, 2009 - 08:37.
how to calculate 45 minute to 60 minute. how can u calculate 45 minute to 60 minute? Log in or register to post comments
Permalink Submitted by aongola (not verified) on November 12, 2009 - 08:48.
backup culculations
I would urge the auther to varify the culculations and the procedure used,i have a load of 15KVA which must be kept active for 2 hrs in case of power failure. with this info i cannot use your procedures to culculate the Ahr for the battery requires.Below wil be of more use to fellow engineers: Number of batteries = N =20 Voltage of each battery = V = 12 V Ampere-hour of each battery (AH) = X Number of Operational hours = T = 2 hrs
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How to calculate UPS battery backup | Backup HowTo
Volt-Ampere = (N * V * X)/ T 15000 = (20*12*X)/2 15000 = 120X X= 125 AH Log in or register to post comments Permalink Submitted by Alaa Noor (not verified) on December 25, 2009 - 02:55.
backup culculations
This calculation does not take into consideation the UPS power factor , and the inverter effeciancy , are you using the batteries to directly supply load ? i.e DC backup system ? or there is a UPS ? if you are using a DC backup , then simply calculate the load current A lead acid battery can supply 100% of its rated current for 30min before the voltage drop to 10.5v and become unusable if you are looking for an hour of backup , limit your load to 60% of the battery rated capacity , 35% for 2 hours, 25% for 3 hours. assuming temp = 25 degrees C. example if you require 60A for one hour , then use a 100Ah Battery @ 25 degree C hope this helps Log in or register to post comments Permalink Submitted by chander (not verified) on January 1, 2010 - 17:12.
battery
hello sir i want to know one think,how to calculate the number of battery we have to used Log in or register to post comments Permalink Submitted by Vanchinathan.P (not verified) on January 5, 2010 - 12:36.
Calculation formula UPS backup time
Sir/Madam, Please give me the formula for calculating the UPS backup time. Also explain me the UPS backup time with the below Given details. Example: UPS Rating = 1500VA No. of Batteries = 2 Battery voltage = 12V Battery rating = 17AH Log in or register to post comments Permalink Submitted by Anonymous (not verified) on January 27, 2010 - 07:40.
UPS Back up time (in Hrs) =
UPS Back up time (in Hrs) = ( DC voltage of battery x AH rating of battery x Efficiency) / VA rating of UPS Assuming that efficiency of UPS is 90%, the back up time for your case is as under; = ( 2 x12 x 17 x 0.9 ) / 1500 = 0.24 hours Say 15 minutes Log in or register to post comments Permalink Submitted by Anonymous (not verified) on January 31, 2010 - 06:57.
how to calculate the ups battery
I want to know on how to calculate the ups battery, example 40 nos. of ups battery, 12 volts of each battery, and 40Ah, how many hours can back up if the power supply is failure. please give me the formula Log in or register to post comments Permalink Submitted by Anonymous (not verified) on February 25, 2010 - 06:09.
Where do you get 15 minutes
Where do you get 15 minutes from YOUR formula dickhead? Log in or register to post comments Permalink Submitted by Anonymous (not verified) on February 25, 2010 - 06:14.
Sorry....let me clarify my
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Sorry....let me clarify my
How to calculate UPS battery backup | Backup HowTo
Sorry....let me clarify my last responce....I see where you get the 15 minutes from the actual formula, but I don't see how you can get 15 minutes. You haven't even considered in your formula floating voltage and end of discharge voltages. I,m sorry to point out a truth...but none of you in this forum seem to have any clue!!! Log in or register to post comments Permalink Submitted by Anonymous (not verified) on March 24, 2010 - 00:00.
UPS Verification
hello there! and I hope someone there can help me with this. I followed you formula to find out how many minutes this UPS will back up. Please let me know what I am doing wrong. UPS specs: 120V AC in and 120V AC. Battery efficiency: 0.83 Battery: (4) 48V, 12 Ah, Sealed maintenance-free, valve-regulated, lead-acid. EBM: "External Battery Module" Battery efficiency: 0.83 Battery: (8) 24V, 9 Ah, Sealed maintenance-free, valve-regulated, lead-acid. UPS has to hold for 30 minutes this load 1638VA. formula: UPS Back up time (in Hrs) = ( DC voltage of battery x AH rating of battery x Efficiency) / VA [(48+24) x (12+9)] x .8/1638 = 0.74 hours about 45 minutes. However the solution that I got from the UPS selector come back with only 35 minutes. The reason I am doing this is because I need to show calculation to show that this UPS would hold the load. Any help would be very appreciated. Log in or register to post comments Permalink Submitted by Anonymous (not verified) on May 4, 2010 - 19:30.
batteries needed
I am trying to achieve 5-7 minutes of back up time for a 300kVA UPS system. Currently the system has no batteries and I dont know what size would work at a full load. Log in or register to post comments Permalink Submitted by rehan (not verified) on May 13, 2010 - 13:59.
backup calculations
Its not possible to calculate the battery ratting through any formula accurately. I have tried different formulas but practically they all become false. Log in or register to post comments Permalink Submitted by Anonymous (not verified) on July 13, 2010 - 16:53.
ups back up time
in yr exapmle 20 nos of 125 ah 12 v are connected in series ? then what will be battery discharge current say at 10000 load practically taken 10kva is max load connected to this ups such that what willbe the back up time Log in or register to post comments Permalink Submitted by Eq (not verified) on July 30, 2010 - 06:09.
This is only a theory.
This is only a theory. Practically, most UPS just don't last, burning their diodes after 20-30 minutes of power outage. The battery degrades over time as well. The main purpose of such UPS - just give you couple of minutes to finish and save your work or initiate server shutdown. If you plan to WORK during power outage, you have to connect gas/diesel generator to UPS. All outages I remember were very short (minutes) or very long (hours). There is no affordable UPS that will survive under load for more than hour. Log in or register to post comments Permalink Submitted by epoxy flooring delhi (not verified) on July 30, 2010 - 10:14.
Nice comment
It is really a nice comment on this post with have a great thought..... Log in or register to post comments Permalink Submitted by epoxy flooring delhi (not verified) on July 30, 2010 - 10:16.
Good mathematics
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How to calculate UPS battery backup | Backup HowTo
I find here a good formula on this nice comment http://www.reliancechemicals.in Log in or register to post comments Permalink Submitted by Anonymous (not verified) on August 2, 2010 - 20:37.
Where do you get 15 minutes
dickhead, 25% of an hour is 15 mins. now no one gonna teach you maths here. Log in or register to post comments
confused
Permalink Submitted by Mustafa (not verified) on August 19, 2010 - 04:24.
Hello, Really what a nice Post. Now I really kinda lost because i want to run both my Compaq laptop and my speed-touch wireless Router for about an Hour, and i really i was hoping if you can let me know a product that would do it, because i really can't figure it out. Thanks Log in or register to post comments Permalink Submitted by tygrus on January 18, 2011 - 03:44.
Battery capacity varies with load
Although a battery maybe rated at X amp-hours you will get less than half of that available when discharged at faster than an hour. A 18Ah @20hr discharge rate can only provide 10.8Ah for 1hr. It’s not that the electrical charge has suddenly disappeared but internal resistance rises, available voltage drops and the devices shut’s off at 10.# volts per 12v SLA battery. You could in theory use 7Ah in the first hour then another 7Ah over the next 6hrs but not the other way around. The other issue is the non-linear efficiency of the inverter and monitoring circuitry. eg. A 1w load will still require .8A or ~20w from the battery, 50w requires 70w, 300w requires 330w, 700w requires 742w from a 24v SLA battery using a 1000w inverter. Most efficient near max load. Inverters may overheat if used at max. load for more than 30mins but the standard batteries don’t last that long at max load. The cheaper the device, the less likely it will handle the extremes. A 150w inverter will keep a 50w load running longer than a 1000w inverter and 50w load connected to the same size battery. Also, after 2 years and 12 deep discharges (run flat for >50% load) the battery will have reduced capacity and may be half the runtime. It’s better to start with 20mins and end up with 10, than to start with 6mins and end up with 3mins. Log in or register to post comments Permalink Submitted by er_satvinder on February 12, 2011 - 23:51.
ups backup time formula
UPS Back up time (in Hrs) = ( No. of DC battery X voltage rating of battery X AH rating of battery ) / VA of ups installed = ( 2 x12 x 17 ) / 1500 = 0.272 hours Say 15 minutes Submitted by Satwinder Singh
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