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Old 05-28-2014
1derer 1derer is offline
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Default 24 volt solar panel for 12 volt battery bank

Though this has probably been addressed a hundred times on this site and elsewhere a hundred times more, I can't at the moment find what I consider a final answer as to what happens when a 24 volt solar panel meets up with a 12 volt battery bank. So far I've heard it would fry the battery like the old battery "boiler" chargers, that if a controller is put between the battery and the panel you'll get charging of 12 volts but for only half the panel's rated watts, or that an mppt charger will make everything right. Does anybody really know?
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Old 05-28-2014
Jim Brookshire Jim Brookshire is offline
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24 volts or more from your solar panels are fine (in fact better) if you have a MPPT charge controller. It will take the higher voltage and convert it to around 14 volts DC to charge your batteries. It will act like a AC transformer - decrease the voltage and increase the amps. Search solar charge controllers and you will probably find a better worded explanation.
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Old 05-28-2014
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MRPutz MRPutz is offline
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http://www.wanderlodgeownersgroup.co...ght=solar+mppt

I'll be running 3 panels in series for a 134.4v (116 VMP) system using an MPPT controller. Just working out the mounting brackets now.

Code:
 
Rated watts                     915
110 F watts                     840
expected charge                 63.5a @ 14.4v
expected input amps              8.41a
VOC                             134.4v
VMP @ 50 F                      116.4v
Classic max current              92a
Classic max voltage            162v
Max design load for this controller = 70%
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Solar = https://www.solarpenny.com/SearchResults.asp?Cat=257

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Old 05-28-2014
mpierce mpierce is offline
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I too, wonder about the watts produced. For you Gurus out there.

If I get a 400 watt, 24 volt panel, and use the required MPPT controller to drop voltage to 12 volts, do I still get 400 watts at 12v, or is it 200, or 800?

Thanks.
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Old 05-28-2014
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MRPutz MRPutz is offline
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Quote:
Originally Posted by mpierce View Post
I too, wonder about the watts produced. For you Gurus out there.

If I get a 400 watt, 24 volt panel, and use the required MPPT controller to drop voltage to 12 volts, do I still get 400 watts at 12v, or is it 200, or 800?

Thanks.
IF.. IF you use a quality MPPT controller you will maintain your watts. The MPPT controllers are basically dc-dc converters with very low power loss.

In my previous post you can see I'm expecting 63.5a @ 14.4v from my 900 watt panels. These panels provide about 8.5a at 35v on the input. So as you see my wattage doesn't really change. That's the beauty of the MPPT controllers. I would suggest Midnight Solar or Bluesky MPPT controllers though. These are tried and known for their quality and performance. Only the Midnight controller (Classic 150) would handle the power & voltages I wanted to run.
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