On-Line UPS

Posted by Ronald Albury on June 06, 2008, 08:49:22 PM

I live in the country and we have *very* dirty power. I've used standard computer UPS devices, but they don't work well enough. They feed the computer with grid power and try to detect when the power fails, and then switches over to the battery.

I want a UPS like they have in industrial situations - the equipment always runs off of an inverter connected to a battery bank and the AC is used to keep the batteries charged. I've heard these called On-Line or Dual Conversion UPS.

Instead of paying thousands of dollars for an On-Line UPS, it seems simple enough to use a battery, an inverter, and a charger. Anyone have any comments?

Ok, now for the second part of this posting. I would like to eventually migrate this set-up to a hybrid system where the batteries are charged by solar when the sun is out, and then by AC if the solar arrary isn't providing enough power. At some point maybe I could even add a wind source.

I've read, in this forum, that you can connect multiple charging sources for the batteries - does that include an AC charger? Is there any special wiring or controller required other than just hooking all of the chargers up the batteries?

Posted by John B on June 07, 2008, 01:42:44 PM

Re: On-Line UPS (Reply #1)

Ronald,

What you're asking for is achievable, but give us some details on what you mean by "*very* dirty power".

I would hazard a guess that 99% of the electrical equipment in your house will work just fine (but maybe not as long!) off a cheap (<$200) 12VDC/120VAC modified sine wave inverter.

Pure sine wave inverters carry a premium price, so you want to be sure that the interference on your power is not from a source within your house before going to too much expense.

Posted by Thomas Allen Schmidt on June 07, 2008, 02:04:42 PM

Re: On-Line UPS (Reply #2)

We are using a Samlex 600 watt 12 vdc "true sine wave" inverter to supply 120 vac to our; computer, tv, vcr/dvd, telephone w/answering, and fax machine. All is well so far after 2 years. Tried a Trace DR 1512 but it messed up the monitor in about a years time. Samlex does not have pass through or charge ability like the DR but you give a little, you get a little and all that.

http://www.homepower.com/home/

Perhaps you are looking for a "true sine wave" inverter that has pass through and charge capabilities. There is quite a few to choose from.
Calculate the amount of power used by all you want to power over a 24 hour period. Most electric products will have a name plate showing volts and amps or volts and watts. Ether way you will want to know watts and for how long it will be in use over 24 hours.
Example: computer takes 80 watts and is in use 10 hours a day. Simple.
10 x 80 = 800 watt hours.
800 / 12* = 67 amp hours. (12* = 12 volts nominal)
67 x 5* = 335 amphour battery bank at 12 volt nominal.
(5* = multiplier that keeps the amount of battery discharge within the top 20% of full charge.)
To replace that 67 amps in one sunny day with PV:
12 x 67 = 800 watts / 4* = 200 watt PV array.
(4* = 4 hours of equivalent full rated charge from a PV module.) Your hours may vary.
http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/

Part 2 - Yes. Obviously, any type of charge going to a battery has to be controlled. Other wise it, or things around it, would catch on fire and burn your house down to the ground. This leads us to the NEC or the National Electrical Code and one reason why there are licensed electrical contractors. As well, there may be required permits before starting any electrical work and inspections by the local authority having jurisdiction. Wether it be city or county or state.

http://photovoltaics.sandia.gov/docs/Design_and_Installation_of_PV_Systems.htm

Size things for the future as well. Because once you see what RE can do, you will want more and more.
http://www.dsireusa.org/index.cfm?EE=0&RE=1

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On-Line UPS

Posted by Ronald Albury on June 06, 2008, 08:49:22 PM

Posted by John B on June 07, 2008, 01:42:44 PM

Posted by Thomas Allen Schmidt on June 07, 2008, 02:04:42 PM

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