# Real newb question on solar



## Dirk Pitt (Apr 21, 2015)

I had posted this in the thread "45 watt panels" I think it got lost in there, that's OK, I should not have interjected into another thread as I did. So I am going to try a new thread of my own on this. 
I can't emphasize this enough I am REALLY NEW to this entire subject and I started with the harbor freight kit, and that is ALL I have - for now.

Thanks for any help.

Original Post
_"I have a harbor freight setup and it is powering one 12V deep cycle marine battery. The only thing I have running on it is a 12v car radio with speakers. I have had zero problems with it and I very impressed with entire setup. I do have the provided lights setup with it also and I use them off and on (no pun intended). My only question is this, at random intervals I hook up by battery charger to it and it shows the battery almost dead. It charges it back up of house 120V. So I am new at this and scratching my head. My little system works, but is seems I need more juice going into that battery. I am thinking about getting another system and hooking it all together. That would be 90 watts. 
Math is not my strongpoint, so please don't hit me with volts x amps x watts x whatever. It is all gibberish to me, I know a little but I need some advice from all of you experts on there."_


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## rstanek (Nov 9, 2012)

what amperage are the solar panels rated for in full sun, it should tell you that in your owners manual, for each 12 volt deep cycle , you should be trickle charging between 2 and 4 amps per hour, any faster you may cook the battery,any less and it won't keep up with demand, demand being a draw of approximately no more then about 2 amps per hour. You need to also set it up so you don't over charge, there are regulators on the market for that purpose. 12 volts x 4 amps = 48 watts , in full sun.....


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## Smitty901 (Nov 16, 2012)

You need enough time for the panels to replace what you use. The control you have is nice in it has the ports. How ever it does not tell you how many AMps you are drawing and how many you are putting back. Latter On the 45 watt thread I will show how I wire two controllers to give me that information. 
Example last night I was drawing .4 amps all night. The over cast sky , then latter full sun was putting between .8 and 2.4 amps back so Easily all that was used was replaced.
The reason the 45 watt thread was started was lot of us are new to this it is so we can learn and share. Fun to play with it all.


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## sideKahr (Oct 15, 2014)

I'll be following the answers on this thread. This is an area I'm become interested in, too.


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## rstanek (Nov 9, 2012)

I have a solar panel for my camper, in full sun it puts out 15 volts , 1 amp per hour, it will not keep up with 2 deep cycle batteries in summer use, in winter you have less sun and more draw.


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## Dirk Pitt (Apr 21, 2015)

I will check the manual on my panels for that information and come back here with it.


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## Smitty901 (Nov 16, 2012)

When your panels are not attached to a load like the battery they will read a higher Out put. As mention the rate it is putting the amps back is what is important.
This pictures shows the battery at 12.8 volt and the panel is putting 2.5A into the battery. That is with good sun. So if you are running 2 efficient lights that are drawing .8 amps . Lets just round it off to 1 amp and you run it 8 hours. The panels would need to return at least 1 amp for 8 hours to bring the battery back to where you started.
At 2 amps it would do it in half the time. This is why the most efficient lights must be used. And why I am sticking with 12 volt rather than an inverter for lights. There is a power loss through the invertor.
In the example I have shown the 2.5 amps was the high for the day it started out early at just under 1 amp. So you can not base you guess on the high numbers.
Also if I wanted to run those same two lights in the bike room, underground no windows during the day time. Long as the panels provide at least .8 amp the would run all day with out running the battery down anything over the .8 the battery would gain.

Notice the black controller the sun symbol with arrow pointing toward the battery that shows what panel is putting in. Touch the selector and then it would show what the battery/load is taking. IMO this is necessary to get a picture of what you can and can not run with what you have. It cleared up a lot of me. This setup is the same as the one Harbor freight sells. It is a 45 watt 3 panel. I did add the second controller to give me information I needed.

solar3 by bob smith, on Flickr


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## PrepperDon (Jan 22, 2017)

What controller is that 


Sent from my iPhone using Tapatalk


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## Smitty901 (Nov 16, 2012)

PrepperDon said:


> What controller is that
> 
> Sent from my iPhone using Tapatalk


 The black one is a Thunderbolt Magnum Item 68738 500 watt From Harbor freight. The are many on the market I can not offer input on long term quality of it . It does work.
I am sure there are many that offer the read outs this one does.
Another thing to be a wear of is trying to recharge to much battery with to little of a panel. Example is the setup I am playing with . The panel seems to have no trouble returning the battery to full charge on a less than prefect day of sun. Long as I do not try to run to much off it. However if I was to attach 2 batteries and run them down what would happen is the system would fall behind and after a short time the batteries would no longer be returning to a full change the system would then start to fail.


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## Dirk Pitt (Apr 21, 2015)

Here is the information on the panels its all I could find in the manual







.


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## 8301 (Nov 29, 2014)

Those panels are designed to charge a 12v battery (which requires about 14.8v to fully charge) and put out about 1 amp per panel. All 3 panels together will put out about 3 amps. If you have a 100 amp/hr battery that is 40% drained math wise that battery needs 40 amp/hrs of charge to completely refill so 40/3 amps= 13.5 hours of good sun to recharge the battery.

but... As the battery gets closer to being fully recharged (above 80% SOC) (state of charge) internal resistance makes charging less efficient requiring more charge energy to fill that last 20%. A basic rule of thumb when charging a battery is that it takes about 115% on the drained energy to completely charge the battery so...
13.5 hrs x 1.15 = 15.5 hours of good sun to recharge that 100 amp/hr battery from 40% DOD (depth of discharge) all the way.

Considering that different battery types have different charging requirements the whole thing can get complicated but that's the short answer.


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## Smitty901 (Nov 16, 2012)

Dirk Pitt said:


> Here is the information on the panels its all I could find in the manual
> 
> View attachment 40369
> .


 With strong sun it will give you about 2.5 amps at14.5 volts. Today I am getting zero no sun fog over cast. It will be a good test as I will run the light all nigh again and see how it goes.
Unless they merge these two thread I will keep posting results in the 45 watt one.


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