Might it make more sense to put all the power gear at the panels and run ac interconnecting wire to the grid tie point and the loads? That way you are only running the ac wires all the way. It will involve a walk to check the system, but might be cheaper in the long run.
Otherwise, what are you using for inverters? Will they charge the batteries from a higher voltage input? 450 volts or so DC off the panels would not be too bad. I expect that a standalone battery charger would be way inefficient and the losses would be high. Most of the stand alone chargers are pretty bad, efficiency wise. Using inverter power to feed an inverter to charge the batteries sounds kinda clunky in the process also, but I think it has been done. Would the receiving inverter accept the power? Hard to say, wouldn't want to buy a bunch and find out otherwise. How about using the Midnite classics in the higher voltage range, and converting it to battery voltage as usual? It might (will) take several but all the other options (controller wise) would probably take as many or more. Some of the Classics will take up to a 250 volt input, that would help to cut down on the copper Just a quick thought stream, Bob Ellison From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Eric Thomas Sent: Sunday, October 02, 2011 12:15 PM To: re-wrenches@lists.re-wrenches.org Subject: [RE-wrenches] Invert first? Wrenches, We are designing a super high end grid-tied w/ battery backup system for a customer. Array will be ~15kW; pole or stand alone structure mounted; 250' from home/batteries. My question is: does it make any sense to invert the power at the array and use this ac to make the long run to the batteries THEN connect to a typical battery charger rather than a dc charge controller? Im mostly concerned with huge dc conductors making this run across the property. Havent delved into the specific design enough to size said conductors yet, or specify any equipment, but wanted to know if im barking up the wrong tree ir not. Thanks for the insight. Eric Thomas Founder Solar Epiphany LLC NABCEP Certified PV Installer WA Electrical Contractor # SOLAREL911NR
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