Posts: 7,734
Threads: 686
Joined: Jun 2011
Everyone knows what a UPS system is... when the power goes out the UPS system runs your AC items off a battery until the power comes back on (or the battery is depleted). They are commonly hooked up to computer systems.
What I'm looking for is the opposite- like a reverse UPS system. Something that switches to AC power when the battery is depleted. I did some searches on amazon and found transfer switches but I'm looking for something more plug-and-play.
Does anybody know if such a product exists? I'm not talking about a whole house solution. Just a single outlet.
Posts: 14,114
Threads: 424
Joined: Aug 2012
This is probably a transfer switch, but it's difficult to tell without more details.
Posts: 3,188
Threads: 216
Joined: Sep 2007
"AC power when the battery is depleted....."
why not go the other way - run the 12 volt system as primary - and keep a trickle charger on the 12v battery using the ac to always keep the battery fresh.
will that work in your application?
Posts: 566
Threads: 22
Joined: Mar 2012
He who hoots with owls at night cannot soar with the eagles in the morning.
Posts: 299
Threads: 49
Joined: Jun 2003
I would think that you could use a control block that is for an automatic start generator to turn on an "ac on" relay instead of the "generator start" relay. See
www.atkinsonelectronics.com and look for GSCM.It will also switch back when charge completed.
Jerry
Posts: 7,734
Threads: 686
Joined: Jun 2011
I "sort of" found what I was looking for on eBay. But I'm still looking for a single-outlet option:
http://www.ebay.com/itm/Reverse-Operation-Automatic-Transfer-Switch-for-Wind-Solar-installations-/261104152477?pt=LH_DefaultDomain_0&hash=item3ccb052f9d
SPECIFICALLY DESIGNED TO KEEP YOU OFF GRID AS MUCH AS POSSIBLE!!!
The EcoTran automatic transfer switch is a unique combination of automatic transfer switch and circuit breaker sub panel. It is designed to take the power input from a 120V feeder breaker in a main circuit breaker panel board, fed by the utility, and from an inverter taking power from a bank of batteries being charged by a wind turbine, solar panel(s), or any other renewable energy source of up 3,000 Watts. As many as 14 branch circuits (120V) can be installed in the EcoTran. These circuits would be prioritized according to the size of the renewable energy source and would include lighting, refrigeration, microwave oven, etc.
The EcoTran is totally unique because it recognizes the renewable energy source (wind, solar, hydro, geothermal) as the primary power source and the utility service as the secondary power source. The EcoTran automatic transfer switch monitors the system inverter and switches automatically to the utility if the inverter is unable to provide adequate power. This means that it will always draw power from the primary system unless the total load on the primary system is temporarily greater than the system can produce. In that case the EcoTran will switch seamlessly to the secondary source (utility) in less than 20 milliseconds and then back to the renewable source, in less than 20 milliseconds, when the temporary increase in power demand has passed. That is fast enough to be unrecognizable to even the most sensitive electronics including cable boxes, clocks and computers. This maximum load management feature prevents inverter overload.
Posts: 3,188
Threads: 216
Joined: Sep 2007
This stuff tends to be pricey - couple of hundy on the low end in my experience. search for "automatic transfer switch" usually start out at about 100 amps.
how big of a load are you switching - another factor will be current draw - are you ok with the switching / sensing element drawing down the 12 volt side? does it need to be UL approved or will something home made do?
I have some bits and pieces laying around if you get stuck.
Posts: 14,114
Threads: 424
Joined: Aug 2012
Yeah, I'm still kinda waiting to hear about the load; if it's small, run it full-time on batteries and use a float charger to make up the difference. This is effectively an "on-line UPS". Side effect is that your load is completely protected from any grid flakiness.
If that load is a computer, it's probably far more cost-effective to convert it to DC. The Targus DC-DC laptop power bricks are well worth the price. For a desktop, order the appropriate picoPSU module from mini-box.com; the WI variants will easily tolerate the "hot" voltage on a PV charge rail. (They even sell a little metal box+fan with screw terminals to replace the AC power supply.)
Active ingredient in a transfer switch is an isolation relay such as this:
http://www.skycraftsurplus.com/relay120v...10amp.aspx
However this is too simpleminded to understand "when battery is depleted", for which you need either a voltage threshhold circuit or (if the batteries are part of a PV system) a charge controller with an LVD output (in which case, the relay needs to match the LVD output, which is probably the battery voltage).
Posts: 3,188
Threads: 216
Joined: Sep 2007
I like these too -
http://www.amazon.com/XANTECH-AC1-Contro...B000NU0T62
problem is: 12 volt draw down. May as well get a 120ac / 12 vdc. regulated power supply with very low idle loss specs.
note the adjustable soleniod voltage
Posts: 7,734
Threads: 686
Joined: Jun 2011
quote:
Originally posted by Bullwinkle
This stuff tends to be pricey - couple of hundy on the low end in my experience. search for "automatic transfer switch" usually start out at about 100 amps.
how big of a load are you switching - another factor will be current draw - are you ok with the switching / sensing element drawing down the 12 volt side? does it need to be UL approved or will something home made do?
I have some bits and pieces laying around if you get stuck.
What I'm thinking (just a thought process and not a "project", at least not yet) is to run something, say a small refrigerator, off a PV/battery setup and since there is not enough juice from the sun to run it full time, have it default back to the grid when the sun isn't out.
