TMG-L ArchivesArchiver > TMG > 2003-06 > 1054848664
From: "myrnice" <>
Subject: Re: [TMG] Comment on UPS
Date: Thu, 5 Jun 2003 17:31:06 -0400
References: <email@example.com> <3EDF9EBC.79C20D54@infoave.net>
Richard & Mickey
Where I worked we has massive battery strings, each 2 volt cell was about 2'
x 2' x 5' high. We had then in various combinations of 24 volt string, 48
volt string, +130 vole string and -130 volt string sometimes several of
these strings in parallel.
We did not depend on these batteries to last much longer than 1 or 2 days.
Most of the time the backup alternators would come online, either nobreak or
sometimes it took as long as 2 minutes for them to power up.
One of the offices I worked in had two 750 KW alternators driven by turbojet
If you really want backup, why not get a small generator to provide AC to
keep the batteries charged for several days if necessary.
By the way, The data center I worked in (a different office) had 9 diesel
alternators that could be synced to and connected to the commercial line if
necessary to help the power company in an emergency. By agreeing to do this
we got a real break on our power bill rate.
"Richard Brogger" wrote on Thursday, June 05, 2003 3:49 PM
Subject: Re: [TMG] Comment on UPS
> Hi Mikey,
> I suggest that you start by recording the watts used by each computer.
> How those figures are combined could be an important consideration.
> You may be able to use one UPS to power three or four computers.
> However, how long the batteries will last will depend on the combined
> load. If your combined load is near the maximum for the UPS, your
> computers will shut down very soon after the power outage begins.
> What is a typical power outage in your area? I live in a wooded area.
> During a storm, the wind may blow a tree into the power line and short
> it to ground. The over current device will open the circuit but the
> automatic recloser will attempt to power the line right away. If the
> tree is no longer in contact with the power line, my electricity is
> restored within seconds. However, if the tree is still shorting the
> power line and a crew has to remove the tree, it can be several hours
> before the power is restored. If the storm was bad and a lot of trees
> took down a lot of lines, it can be days before they restore my power.
> In all but the first case, I have to finish what I am doing and shut
> down my computer or have it shut down by the UPS. Once the computer is
> off, it remains off until I turn it on. If your area commonly has
> power outages that last several minutes, your computers will be shut
> down until you return unless your battery capacity is sufficient to
> carry the load long enough.
> UPS come in a wide variety of sizes for computers but those are
> produced in large quantities and thus are inexpensive. Once you go
> above the load for home computers, the number of units sold diminish
> and cost per unit rises rapidly. 10 KW UPS are common in my work. They
> are usually powered by a battery bank with 200 cells and each cell can
> cost over $3000.
> A UPS system consists of three items, a battery to supply the power
> during an outage, a battery charger, and the inverter to convert
> direct current to alternating current. When these three items are
> built and sold as a packaged unit, they are usually below 1000 VA
> capacity and have relatively small batteries. However, due to the fact
> that truckers have been buying inverters in the 2 or 3 KW range, the
> cost of these inverters has come way down.
> A 2 KW inverter can be purchased for about $250 and that is plenty for
> nine computers. The next item is enough battery capacity to power the
> inverter and this part gets expensive in a hurry if you need high
> current draw for long periods. I use 12 volt, deep-cycle marine
> batteries. These are built to supply high current. Although golf cart
> batteries are also deep cycle, they are not designed for high current
> and should not be used above 20 amps for either load or charging.
> 1800 watts at 120 volts will be 15 amp draw on the inverter. If the
> inverter were 100% efficient, the draw at 12 VDC would be 150 amps. A
> battery bank of 6 volt golf cart batteries that has two batteries
> paired in series will supply the 12 VDC that is needed but it will
> take 8 pairs in parallel to supply the needed current without
> shortening the life of the batteries. About four years ago, a 950
> amp-hour golf cart battery was $90. I would guess that if I bought 16
> at today's prices, due to the quantity, I might still get all 16 for
> Using eight 950 amp hour deep cycle marine batteries will cost about
> $1250 for the same total amp hour capacity. In theory, either battery
> bank should be able to supply the inverter for two days. However,
> inverters are not 100% efficient. On the flip side, I do not draw 1800
> VA all the time and those batteries would last well over two days.
> Since I do not need that much capacity, four 950 amp hour deep cycle
> marine batteries will work for me.
> A 40 amp battery charger for an RV costs about $135. While that
> charger is too small to make the whole system work like a 1800 watt
> UPS, it should meet the average normal load. With such a system, I can
> power my computers but I can also have lights and run the LP furnace.
> If I shut down part of the load, I can run the microwave oven. i.e.,
> with just over a grand invested, I will be able to use my computer,
> have lights, heat, and hot food. I have everything except that I need
> two more batteries to extend the use period.
> Since I do not need to leave my computers powered while I am gone, my
> needs are not the same as yours. However, you might be able to adapt
> these ideas to meet your needs. Such a system might be better than a
> lot of UPS that serve just one purpose. Invest some more and solar
> cells could charge your batteries.
> Richard Brogger
> Mikey wrote:
> > > > By "away from your computer" I mean out of the house, where
> > > > you would not realize an outage had occurred or are too far
> > > > away to get back to shut down your computer before the UPS
> > > > battery is exhausted.
> > > > Terry Reigel
> > >
> > >
> > >BTW, using your definition, I *never* leave my computer
> > >running unattended. Ever.
> > >Darrell
> > >
> > I leave my 9 computers running 24/7/365! I even leave them on even while
> > vacation! They are running small Distributed Net programs. Like helping
> > find the cure for cancer, finding a cure for smallpox, finding extra
> > terrestrials, etc.
> > I do not presently have a UPS, if the computers go down they go down,
> > am considering one.
> > This leads to my question......is there a UPS that is better than
> > Do I need one for each computer, all are desktop types, except one that
> > a server(not doing server type stuff), or will one work for several or
> > all? I do not run TMG while I am away on any of those computers, just on
> > laptop or PDA that I have with me.
> > Have you checked your Smoke Detector battery, LATELY?
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