# question about using grid tie panels for 12 volt



## budgetprepp-n (Apr 7, 2013)

Hi,
I got a great deal on 2 panels they are 235 watt each with 29.44 volts . So I think they are for grid tie in.
If I use these with a mppt controller for my 12 volt battery pact what could I expect to get out of these
as far as watts and amps?


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## Montana Rancher (Mar 4, 2013)

The thing to understand is Watts x Amps = Volts

OR Watts/Volts = Amps

In other words your 235w panel at 29 volts will give you about around 8 amps of power

Keep in mind that the "volts" is at maximum sunlight, so on an overcast day it will be 40-50% of the rating

Therefore think of this panel as 4 amps per hour (when the sun is shining)

in the summer is shines almost 12 hours a day, in the winter where I live it is 6 hours a day.

So let us figure 6 hours a day x 4 amps is 24 amps which will run a typical chest freezer about 12 hours.

So 2x of these panels will run a chest freezer all day.

I'm talking rough figures as the temperature and total sunlight makes a big difference.

Currently I am running 2x chest freezers (total 48cf) my 220 volt 1hp well pump and my very current refrigerator (freezer drawer on the bottom) on a 3750 watt system on a 48V battery MPPT at 45 Degrees Latitude with no problem.

That is 15 of your solar panels but mine are 250 watts each.

IT IS NOT cheap, but unless we bet a EMP I will be golden for frozen meat and refrigeration.


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## HuntingHawk (Dec 16, 2012)

There is no difference in panels between grid tie & off grid. Its the controller that is the determining factor. The panels you purchased are for a 24V system versus a 12V system.


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## Prepadoodle (May 28, 2013)

Montana Rancher said:


> The thing to understand is Watts x Amps = Volts


Actually, watts/amps = volts.

watts = amps x volts; amps = watts/volts; volts = watts/amps

The only other thing I would add is that the panel orientation is also important. You want the sun to be hitting the panels at 90 degrees for max power. If you are planning a fixed installation, it's usually best to orient the panels so they take maximum advantage of the winter sun angle. This will help you gain more power when the days are shorter.


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