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Posted by Morris Dovey on September 20, 2009, 12:17 am
 
AES wrote:


You might consider something like

    http://www.iedu.com/DeSoto/Projects/Monitor/

Note that I left the ethernet port available...

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

Posted by AES on September 20, 2009, 8:02 pm
 
wrote:


Thanks!  WIll look at this . . .

Posted by Randy on September 20, 2009, 3:17 am
 
"> I'll agree with all of the above reply to my post -- except that I'm

Sorry about the word "demand", I have had so many people talk about how they
are going to wait untill this technology is proven that I roll my eyes too
soon.
I am sorry to hear about your roof experiance, my original roof (shake
shingle)lasted from 1924 till 1993 when I noticed some breakage but no
leaks.This roof should last till my house gets torn down by an ever growing
nursing home to the south.


I am not an expert on the grid tie no backup systems but I'll give it a try.
Grid tie inverters use D.C. voltages in the 195 to 550 range so perhaps
tapping
from the panels using bypass switches and separate charge controllers to
charge the battery. Difficult but workable.
Samlex makes this:
http://www.altestore.com/store/DC-Voltage-Converters/Samlex-72-144V-Input-12V-Output-275A/p2526/
Which may help, or you can contact Samlex to see if they make higher voltage
units.
If you change your mind about buying a more complex setup, Outback, Xantrax
and I believe SMA make grid intertie inverters with battery backup. I like
my Outback.
The batteries don't have to be huge, cheap car batteries will work if all
you want is the power to be on during a daytime power outage. However I
prefer big batteries.
Outback has came up with the Smart RE system that looks rather uncomplex
but expensive.
Also there are programs and equipment that measure system performance for
many systems but as far as photometers, I am unfamiliar with those devices.
I usually just use those really huge photocells mounted on the roof hooked
up to the charge controller/ data hub/computer for logging system
performance.
I do agree that a small battery charging curcuit would indeed be handy but I
guess inverter manufacturers would prefer that the solar installer work with
the customer on the power backup issue before making the purchase when the
cost differance is more minimal.

Hope this helps
Take care
Randy



Posted by AES on September 20, 2009, 8:09 pm
 

Tar and gravel on flat or Eichler-style slightly sloped roofs,
especially in hot, sunny UV-drenched areas, can be hell to maintain
(especially if people insist on walking around on them a lot).



Your response is very interesting -- I'll look into these ideas.

Posted by Russ in San Diego on September 20, 2009, 11:09 pm
 
You can have grid tie AND battery backup if you want -- but you have
to use an inverter that is designed for this purpose.  I have a
Xantrex SW4048 that does this.  It uses a 48-volt DC system.  I use
Outback "charge controllers" to maintain the panels at their optimum
production voltage (typically 57-62 V) and feed the DC system with
what the batteries want to see (more like 52-53 V).  I have 24 T-105
6V 225AH deep cycle battries in 3 banks of 8 series strings.  My first
batch lasted 8 years, the first 5 of which they were being operated at
a bit higher voltage than optimum due to the original C40
controllers.  I'm hoping the new batch of batteries will last longer,
especially considering that the price of T-105s has more than doubled
since I bought my first set...

I don't think you'll have any luck finding a primarily grid-tie
inverter that happens to have a little DC capacity for charging a
couple of batteries.  The way to do that would be for you to just use
a grid-tie-only inverter and plug in a trickle charger, like anyone
else.  You would then hook up your DC-powered devices (including a
small inverter) to your batteries, if that's really what you want.

I bought our battery-backed, grid-tied PV system when I recognized the
California deregulation mess whose outrageous legislation was written
by the electric power lobbyists and further warped by the legislature
-- and when I learned of the substantial rebates that were available
at the time.

Rolling blackouts and skyrocketing rates aren't (currently) the threat
they once were, but I'm still happy to have my electrical power
security.

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