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

[Glenn Burt]

There is a way to override the first battery preservation mode that the SI
enters to allow a brief period of operation before killing the batteries
(all programmable setpoints) which would allow charging again.

 

-Glenn

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of
william at millersolar.com
Sent: Sunday, February 09, 2014 3:51 PM
To: 'RE-wrenches'
Subject: [RE-wrenches] Min grid with no direct DC charging

 

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
<http://www.solarindustrymag.com/digitaleditions/Main.php?MagID=3&MagNo=54>
&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

 

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