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Must Battery Backup System be close to the Electrical Main?

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Posted by Ira Serkes on June 16, 2006, 5:11 am
We will be installing PV and Battery Backup in a few weeks.  The
initial location planned for the Battery Backup System is about 10'
from the main, which will not be a cosmetically good place to put it.

I'd like to place it in different location, which would also be easier
to access.  To do so would mean that it's about 30 ft from the main...
so it would result in a 60 ft longer wiring run.  30 additional ft from
the PV cells to the Battery Backup, then 30 more feet back to the main.

Other than the extra cost of running conduit, what are the pros and
cons of locating the Battery Backup system so far from the main?  Is
there a big efficiency or power loss?

Ira Serkes ira@berkeleyhomes.com

Posted by Rheilly Phoull on June 17, 2006, 1:00 am
Ira Serkes wrote:

I guess there is no loss in efficiency if ya do it right but thats the rub,
the extra costs :-)
Incidently, you really dont have ta go into such detail of the proposed
installation, we all read minds on this NG   !!


Cheers ......... Rheilly P

Where theres a will, I want to be in it.

Posted by Jeff on June 18, 2006, 4:59 am
 Rheilly Phoull wrote:

Size the wire up. Wire loss is dependant on the current and the
resistance of the wire.

Volts (lost) = I (current) * R (resistance of wire).

Power lost is I * I * R.

For the same power, current at 12V will be 10 times what it would be at
120V.  So, you'll want to worry about the loss in your low voltage DC
circuit more than the loss in the mains.

   Here's some wire resistance values:

<URL: http://www.amasci.com/tesla/wire1.txt  >

Remember that is for just one wire so double it.


Posted by walter_lee on June 22, 2006, 3:46 am
 Normally the thicker the (copper) wire the higher current
rating.The resistance of the wire is based on the thickness/cross
section of the wire (bigger the better) and the length of the
wire/cable (the shorter the better).  After looking at several
solar homes at the Solar Decatholon in DC, my opinion is the
foremost aspect for the layout/design of a battery storage
area is that it be properly ventilated, the battery areas
should be acid resistant, it should be easy to monitor the
batteries,  and that it should be easy to replace
either the cables and the batteries.

Jeff wrote:

Posted by Ira Serkes on June 18, 2006, 8:12 pm
 Ira here.. thanks for the tips... have solved the problem!

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