UPS Watts and Run Time
UPS Watts and Run Time
(OP)
Ok I am confused I must just be lacking knowledge in how these things work.
NOW with my own personal battery packs I know if I have a 3 amp battery and I put a 1amp load in theory that battery will operate that load for 3 hours. I do this all the time.
NOW I have a 200watt ups. I plugged my server into this UPS the server only consumes 74 watts. now by my math 200 watt battery 74watt load means nearly 3 hours but at least 2 hours run time (74x2=148watts) assume the other 52 watts is overhead etc.. but most UPS's measure there run time in MINUTES at even half load (full load should be 1 hours half load should be 2 hours ???) what am I missings ?
What I suspect is that a 300watt UPS is not actually 300watts.
Example I can take a 1amp battery and DRAW 20 amps from it and it will work fine for 1/20th of an hour.
This implies to me its NOT a 300watt capacity battery inside the unit. How do I determine what the ACTUALLY watt capacity of a battery is (IE what load will run for 1 hours) I want a battery capable of 5 times 74 watts so I can run the machine for 4 hours if the power goes out.
Suggestions ?
Thanks!!
Chris Taylor
NOW with my own personal battery packs I know if I have a 3 amp battery and I put a 1amp load in theory that battery will operate that load for 3 hours. I do this all the time.
NOW I have a 200watt ups. I plugged my server into this UPS the server only consumes 74 watts. now by my math 200 watt battery 74watt load means nearly 3 hours but at least 2 hours run time (74x2=148watts) assume the other 52 watts is overhead etc.. but most UPS's measure there run time in MINUTES at even half load (full load should be 1 hours half load should be 2 hours ???) what am I missings ?
What I suspect is that a 300watt UPS is not actually 300watts.
Example I can take a 1amp battery and DRAW 20 amps from it and it will work fine for 1/20th of an hour.
This implies to me its NOT a 300watt capacity battery inside the unit. How do I determine what the ACTUALLY watt capacity of a battery is (IE what load will run for 1 hours) I want a battery capable of 5 times 74 watts so I can run the machine for 4 hours if the power goes out.
Suggestions ?
Thanks!!
Chris Taylor
RE: UPS Watts and Run Time
What you need to do is figure out how many watts your load will draw. Then grab the manufacturers specs for the battery, and work out your watt/aH/cell figures from that. If for example you download a Yuasa manual it should have the kind of table you need on page 7.
RE: UPS Watts and Run Time
ht
If you graph them you will see they are not a straight line but more like a ski jump curve (to be specific it is a power curve)
They also have a selection engine that will get you to the right UPS
http://www.apc.com/tools/ups_selector/index.cfm
RE: UPS Watts and Run Time
You're confusing instantaneous watts, vs measured energy in watt-hours. A UPS can say that it is a 300 watt unit - meaning that it will support a 120 volt load, with perhaps 2.5 amp current draw. It does NOT say how long it will support that load - or if it does, it mentions runtime in minutes. many UPS intended for serious commercial use have optional add-on battery packs, so you buy the UPS for the amount of current it will have to supply, and you add battery capacity to add time that the unit will support that load.
At a previous job, in a law firm, I had a 5KW Ferrups, with four big wet-cell storage batteries. The software with it let me know what the load was at any given time, and how long the intalled battery pack would support that load. As I powered down equipment, the runtime reading would increase. Normal daily load would give me maybe 30 minutes runtime. When our building did it's annual powerdown, for about 24 hours, I powered down all the servers, but left the routers and T-1CSU/DSU's running, so I woulnd't have to restablish all the T-1 connections whent he building came back up. w\With just routers and T-1's for the load, I had a runtime more like 40 hours, which saved me a lot of work when the power came back up.
I hope this helps you understand UPS's better. Think of a flashlight that can run on AAA, AA, C, or D batteries. All the batteries have the same voltage, but contain more milliampere-hours of energy. Given the same load, the bigger battery will keep the light lit longer. for a given battery, if you use a bulb that draws less current, it will run longer. That's why the new LED flashlights are so neat - much more light, much less battery drain.
Fred Wagner
RE: UPS Watts and Run Time
YES LED's Rock. I only have LED flash lights. my 4000+ bulb christmas lights were 100% LED and my bedroom and both bathrooms are 100% LED.
RE: UPS Watts and Run Time
Fred Wagner
RE: UPS Watts and Run Time
I walk into a radio shack and it says right there on the boxes 6amp/hr 9amp/hr etc.. thats all I wanted from them
RE: UPS Watts and Run Time
Fred Wagner
RE: UPS Watts and Run Time
You can normally find what battery your unit has in it by either downloading the manual for the unit, or going to a website like http://www.batterywholesale.com/ (where I buy my batteries) and find what replacement battery your unit takes.
Most manufacturers also publish run time charts that show run times for a particular unit at varying loads.
RE: UPS Watts and Run Time
As I have learned from some UPS specialists calculating any expected remaning power on the UPS over 25 min will never be correct.
Don't remember for sure why, and at that time it did sound very strange for me.
But I have gotten the explanation more the once.
Last time I got the explanation was a year ago when I needed to plan to have 160KVA redundant for 90+ min.
As stated before the power factor can be tricky. It is difficult to understand, but also difficult to get real information from the server vendors on that you can use.
UPS and power in general is tricky and thank God that UPS, Power, cooling and Diesel isn't part of my job any more.
/johnny