[RE-wrenches] Small battery bank vs too large array

[Chris Mason]

I did a similar system for a client, in a place where grid connections were
not very legal. We powered s sub-panel but the power exported was used in
the rest of the house.
If you use 4 x 250Ah batteries, a 60A controller is not going to over
charge the batteries as they have a 65A charging limit so you don't need to
get into homegrown solutions.
2KW PV will only give you 40A @ 50V
The system will send the excess to the grid (We did grid tie).
The grid will take over if you have an outage.
The system will revert to grid once the battery level falls below a setting
- we used 44V.
It works well and is inexpensive to do.



On Thu, Jul 19, 2012 at 5:20 PM, Drake <drake.chamberlin at redwoodalliance.org
> wrote:

>  Hello Wrenches,
>
> Where can I get a device that will measure current through a shunt and
> create a signal to trigger a relay?
>
> We want to be able to use a 2 kW array with four, 200 AH sealed batteries
> on an Outback system.  2 kW of PV would be too much amperage for the
> batteries.  The idea is to open relays to disengage strings in conditions
> of high current to the batteries.
>
> The reason for this is to create backup systems where power will be
> abundantly available when the sun shines. The system will normally connect
> to the grid, except during outages.  In normal charging conditions the
> power will go straight to the grid.  When the grid is down, power will be
> available for loads and battery charging, but batteries will be protected
> from overcharge?
>
> Any suggestions on ways to accomplish this are welcome!
>
> Thanks
>
> Drake
>
>
> Drake Chamberlin
> *Athens Electric LLC
> OH License 44810
> CO License 3773
> NABCEP Certified Solar PV Installer
> 740-448-7328
> *http://athens-electric.com/
>
> _______________________________________________
> List sponsored by Home Power magazine
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> Options & 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
>
>
>


-- 
Chris Mason
President, Comet Systems Ltd
www.cometenergysystems.com
Cell: 264.235.5670
Skype: netconcepts
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20120720/8898346a/attachment-0004.html>