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Mielmari

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Posts: 3
Reply with quote  #1 
Hello,
I am totally new to the subject: I need to mount a solar panel power supply to power a 12V 3-5A device (3A will probably suffice, but it may be good to leave a margin of up to 5A), so that it works for 3 hours every day.
- What panel do I need?
- what regulator?
- what battery?


stmbtwle

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Posts: 2,907
Reply with quote  #2 
How "vital" is this equipment?  Can you stand to have it shut down for a couple days due to bad weather?

Another problem is location.  Solar power is location dependent.  The power available in say Juneau is NOT going to be the same as it is in Quito.  Without a location everything else is just a guessing game. 

Given your specs I'd say you need maybe 15 amp-hours per day.  A better U1 battery can do that without much problem, but if the weather is bad you probably should have a group 27 or 30 deep cycle "marine" battery.  That should carry you for 3-5 days without sun. If you REALLY want reserve, look into a pair of GC2 batteries.  They're 6v, which is why you need two (in series). 

Battery type: AGM is maintenance free and arguably better than flooded, but also more expensive.  Then there's Lithium.

Charging... What you take out, you have to put back in... Better to have more than not enough.  So I'd go with about a 100w panel, they're pretty common. You can even buy "kits" that include everything but the battery.

A 100w panel puts out about 7 amps or so, and you can find any number of PWM controllers in the 10 amp range on Ebay or Amazon. They're not expensive.

You'll want to monitor your battery voltage, so if the controller doesn't have that capability you'll want a voltmeter as well, they're available for a few dollars on Ebay as well.

Hopefully others will come up with their recommendations, and you can choose what looks best for you.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Mielmari

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Posts: 3
Reply with quote  #3 
Thank you very much, stmbtwle, for answering.

My equipment is not vital. It would be located at latitude 42.8100 (north of Spain).


It should work only on sunny days (during sunny hours), towards the end of spring  or early fall.

It is a project that has to do with the activity of honey bees.



stmbtwle

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Reply with quote  #4 
Very possibly you could eliminate the battery altogether. 

A charge controller will not work without a battery and the high output voltage of the panel may damage some electronic components if hooked up directly. HOWEVER I have used a 24v-12v voltage reducer to convert the panel voltage to a safe 12 volts. Some, made for golf carts, are waterproof and adjustable.

https://www.ebay.com/itm/153250645033

Eliminating the battery makes it automatic, as well.


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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Mielmari

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Posts: 3
Reply with quote  #5 
It is good news!

What type of panel should I use? I mean the characteristics that should have: size, power ... (I do not know these issues)

stmbtwle

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Reply with quote  #6 
12v, 100w (mol) pv panels are pretty common and not too expensive. 24v, 200+w panels may seem to be cheaper, but the freight can be more than the panel. Smaller panels can be attractive too as you can add more if needed for not much cost. See what's available and decide accordingly.

A lot depends on the voltage required by your equipment. You haven't said but I guess 12v. Bear in mind that "12v" panels can (and will) put out over 21v under certain conditions. A fan motor might take it, but sensitive electronics may not, thus the voltage reducer.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
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