Wrenches The ability for proper charging has always been an issue way back befor ac coupling was a thing. Its near an uncontrolled charge and if you tank the batteries and shut down that's it no charging from the ac coupling component Jerry
Sent via the Samsung Galaxy S™ III, an AT&T 4G LTE smartphone <div>-------- Original message --------</div><div>From: Ray Walters <[email protected]> </div><div>Date:08/20/2015 6:56 PM (GMT-10:00) </div><div>To: RE-wrenches <[email protected]> </div><div>Subject: Re: [RE-wrenches] AC Coupled with Generator </div><div> </div>Hi Folks; I've done more research on the whole AC coupled issue, and one flaw I found with both the Sunny Island and the Radian is that they can't really do a full 3 stage charge for the batteries in off grid mode. They detect that the batteries are full and disconnect the AC coupled GT inverters, but this is about as subtle as the very early charge controllers, and amounts to 1 stage charging. This is fine for temporary outages, and when the grid comes back, the batteries get a good 3 stage charge. But these folks are really wanting a design that could be taken off grid permanently. Also as you my recall, the GT PV system is Enphase, so we can't use the more sophisticated controls that SMA offers for the Sunny boys. I hate to say it, but I might be back to a diversion load with PWM controller. Not elegant, but we could get 3 stage charging. Every time I look at AC coupled setups, I just want to start over with charge controllers. R.Ray Walters CTO, Solarray, Inc Nabcep Certified PV Installer, Licensed Master Electrician Solar Design Engineer 303 505-8760 On 8/17/2015 9:39 PM, Mac Lewis wrote: Hi Ray, With that size grid-tied system, you would want to use a battery based inverter(s) near the (6.7/0.8) 8000W range. The frequency shift of the Sunny Islands will work with kicking out the enphase inverters but you wouldn't get the same output ramping that it would offer if it was a Sunny Boy grid-tied inverter. The Sunny Island can effectively solve your generator backfeeding because there is a reverse current sensor that will disconnect the AC input at whatever level you want, 50 mA is default I think. You may need to give the Sunny Island generator start control for this however. You can read about it here on page 137. http://files.sma.de/dl/15216/SI4548-6048-US-BE-en-21W.pdf You'll need to give the Sunny Island a digital signal that tell it whether its connected to a generator or a grid as outlined in the manual. This is where the Radian is nice because it has two AC Input terminals. Sounds like an interesting project. Good Luck. On Mon, Aug 17, 2015 at 8:36 PM, Jerry Shafer <[email protected]> wrote: I cant see this working well without some battery based inverter Jerry On Aug 17, 2015 10:10 AM, "Ray Walters" <[email protected]> wrote: HI Esteemed Wrenches: I am consulting on a system I have never seen, that consists of a 6.7Kw Enphase roof mounted system, and 2 backup generators. Each generator has an automatic 200 amp transfer switch to back up its own 200 amp panel. Both 200 amp panels are fed by a 400 amp service from the grid. The Enphase PV backfeeds a subpanel in another building which then is fed by a 2 pole 60 amp breaker in one of the 200 amp panels. Currently they are having issues with the generators kicking out because of the Enphase inverters. That part I understand: you can't backfeed a generator, or its voltage regulation freaks out. Now we get to the fun part: they want to create a third critical load subpanel with loads selected from both 200 amp panels to be powered by batteries and an inverter. I am considering the Sunny Island since it makes the most sense with its ability to signal the Enphase inverters to shut off when the batteries are full. I also see this as a partial solution to the generator issue, since normally the Enphase will be connected to the output side of the Sunny Island. However, when the generator is used to charge, we will be back to directly coupling the generator output to the Enphase. Here are some possible solutions I'm considering: 1) Use a separate charger for the generator so that it will only feed DC to the batteries, and not be AC coupled. 2) convert the PV back to DC with charge controllers, but that would involve ditching and adding another conduit run between buildings. 3) Put the Enphase PV on a relay that would disconnect the PV when charging with the generator. 4) Something I haven't thought of that one of you clever folks can suggest...... As always, thanks in advance for all you responses, -- R.Ray Walters CTO, Solarray, Inc Nabcep Certified PV Installer, Licensed Master Electrician Solar Design Engineer 303 505-8760 _______________________________________________ List sponsored by Redwood Alliance List Address: [email protected] Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/[email protected]/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org _______________________________________________ List sponsored by Redwood Alliance List Address: [email protected] Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/[email protected]/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org -- Mac Lewis "Yo solo sé que no sé nada." -Sócrates _______________________________________________ List sponsored by Redwood Alliance List Address: [email protected] Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/[email protected]/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
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