[RE-wrenches] Charge Control in AC coupled system

[Howie Michaelson]

Hey Mark,

Thanks for the proprietary info!

However, I'm wondering what prevents the batteries from getting cooked
over a period of time if there are light or no loads in the house and lots
of sun.  I understand that the relays will divert more and more power as
voltage increases, but if there is enough sun to keep the voltage elevated
even with the diversions, but not enough to trip the final relay, then it
seems the batteries could still potentially get over charged over the
course of several sunny days.  I realize that this is not a great
likelihood in most circumstances, but knowing my luck...

Howie
-- 
Howie Michaelson
NABCEP Certified Solar PV Installer™

Sun Catcher, LLC
Renewable Energy Systems Sales and Service
VT Solar & Wind Incentive Program Partner
http://www.SunCatcherVT.com
(cell) 802-272-0004
(home) 802-439-6096


On Thu, October 28, 2010 4:32 pm, Mark Dickson wrote:
> We have done one this way and came up with a good solution that has been
> working great for two years now.  However, this is proprietary
> information,
> so tough . . .!
> Just kidding. . .
> We used a Morningstar Relay driver to control 3 different "dump loads"
> that
> turn on at consecutively increasing battery voltages.  The fourth relay
> that
> kicks on is one that cuts the Outback's AC power to the Sunnyboys and
> shuts
> the solar down just in case the dump loads fail or if they are getting way
> more solar than they can utilize.  The dump loads that come on prior to
> this
> are various heaters and ice melt systems.  These dump loads work out great
> since the customers are only there in the summer and they rely on these
> heaters to keep their fancy home from freezing in the winter.
>
> Best regards,
>
> Mark Dickson,
> NABCEP Certified Solar PV Installer T
> Oasis Montana Inc.
>
>
> -----Original Message-----
> From: re-wrenches-bounces at lists.re-wrenches.org
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Howie
> Michaelson
> Sent: Thursday, October 28, 2010 2:00 PM
> To: RE-wrenches
> Subject: [RE-wrenches] Charge Control in AC coupled system
>
> Hi All,
>
> I have done several AC coupled off-grid systems using Sunny Islands and
> Sunny Boys, but I am now doing one with a dual stacked OB VFX3648 (with a
> PSX240 on the Inverter out for load balancing) and a SB3000.  There is
> also an existing array that is running through an MX60.  What I am
> wondering about is how folks have set up AC coupled string inverters to
> best utilize the solar gain while not toasting the batteries.  I'm a big
> fan of the tapering control offered by SMA through the frequency shift of
> the SI's, but that's not available here.  What relay/contactor setup have
> folks found most efficient and safe?  Thanks in advance,
>
> Howie
> --
> Howie Michaelson
> NABCEP Certified Solar PV InstallerT
>
> Sun Catcher, LLC
> Renewable Energy Systems Sales and Service
> VT Solar & Wind Incentive Program Partner
> http://www.SunCatcherVT.com
> (cell) 802-272-0004
> (home) 802-439-6096
>
>
>
>
>
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