Re: [RE-wrenches] Min grid with no direct DC charging

[Allan Sindelar]

William, Years ago I designed a large SB/SI system for a high-mountain lodge but never got the job, so this is not tempered by experience. (Years later I was hired as a third-party consultant to review the suggested upgrade to the installation when it didn't work as contracted, but that's another story.) John Berdner was my SMA design resource at that time. He recommended including a relatively small amount of DC-coupled battery charging through a charge controller, specifically to provide protection aginst the situation you have identified. Allan Allan Sindelar al...@positiveenergysolar.com NABCEP Certified PV Installation Professional NABCEP Certified Technical Sales Professional New Mexico EE98J Journeyman Electrician Founder, Positive Energy, Inc. A Certified B CorporationTM 3209 Richards Lane Santa Fe, New Mexico 87507 505 424-1112 office 780-2738 cell www.positiveenergysolar.com   On 2/9/2014 1:50 PM, will...@millersolar.com wrote: Friends:   I have  inherited an off-grid install gone wrong.  This is a mini-grid with Sunny Islands and Sunny boy inverters.  All of the PV is connected in AC coupled mode.  There is no direct DC battery charging through a standard charge controller.  Is there any downside to this?   Thinking through possible scenarios, I see a problematic situation:  The generator is out of order and the batteries are depleted.  The loads are all turned off to allow the batteries to recharge, but the battery voltage is so low that the Sunny islands will not start up.  Therefore there is no grid and therefore the Sunny Boys will not start and provide PV.   Is this scenario valid?  Any other “gotchas” I have not described?   Thanks again to all of you out there.  It seems my work flow is such that I come up with a quantity of questions all at once and I feel bad I am periodically loading the forum.  I always try to research and think these things out before I come to the group.  I found this and it seems to reinforce my suppositions above:  http://www.solarindustrymag.com/digitaleditions/Main.php?MagID=3&MagNo=54  I think the bottom line is that the most reliable system will have a majority of the PV AC Coupled with have a modest RE component DC coupled.   Sincerely,   William Miller   _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org

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