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Learning Project Help - Converting a full sized solar panel

driscolldb

Aug 24, 2018
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Hello,

I'm just getting into electronics and thought I'd make something useful, and hopefully easy.

I'd like to take a full-sized 100W solar panel and turn it into a USB charger, without battery storage or charge controller. Much like the available portable solar phone chargers, except on a much larger scale, and not so portable. Its going to sit in a window and keep a bunch of usb flashlights, radios, and phone battery banks topped off. It might also be taken to various outings.

I plan to drill and cut into the casing of the panel to add as many 5V 1.5A female USB ports as realistically possible. I'm not looking to fast charge anything, nor do I need abysmally slow charging.

The panel:
100W 18.2V 5.49A

The ideas I've had include chopping up a bunch of car cigarette USB outlets and wiring them into the panel, or stepping each and every outlet down with something like an IC7805.

This will be an all in one unit so it will sit in the sun and heat dissipation will be a factor. I may just run cable from the panel to an outlet box so that the panel can sit in the sun while the devices being charged sit in the shade.

So, my questions are, is this realistic? How many USB outlets could I expect to get out of this? Should I step up power up to get more?

Any design ideas and help is very much appreciated.

Thank you and respectfully,

David
 

Bluejets

Oct 5, 2014
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Might be a good idea for you to do some reading on solar panels and their characteristics and requirements for an output controller.
One is an open circuit panel can deliver in excess of 80 v dc which can give a nasty wack or worse.
 

driscolldb

Aug 24, 2018
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A single 100w solar panel, rated at 18V can put out 80v dc?

My home solar system is 48V and I have to connect several in series to get that high.

I may not be understanding you.

Thank you,

David
 

WHONOES

May 20, 2017
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You need to look into battery charging methodology before you do anything else. Form the tenet of your first post, you don't seem to appreciate what is involved and what the pitfalls / dangers are.
 

driscolldb

Aug 24, 2018
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WHONOES,

I don't see how you could assume that I don't appreciate pitfalls and dangers when I'm here stating that I'm learning with a new project, asking advice and having not done anything yet.

My specific questions were on realism and expectations. It also concerned fast and slow charging and how to accomplish it.

If your suggestions are to go take a class, this forum is useless to anyone who wants to get into this a little.

David
 

Bluejets

Oct 5, 2014
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A single 100w solar panel, rated at 18V can put out 80v dc?

My home solar system is 48V and I have to connect several in series to get that high.

I may not be understanding you.

Thank you,

David

I did say open circuit voltage which is what you will be dealing with, part of the time at least from what you have said in original post.
Btw...my home solar system is over 480v dc, in circuit.
 

WHONOES

May 20, 2017
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It was because you seemed to think that you can charge a battery using just a 5 volt regulator.
The suggestion was not to take a class. You can google battery charging. There is a wealth of info out there.
 

driscolldb

Aug 24, 2018
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Whonoes,

I don't intend to just charge batteries with this system. The standard input I read is 5v 1.4a so that what what i was going off off.

The Internet is a wealth of information. This forum was part of it. In searching that wealth of information I ended up here and am now being told look elsewhere. Does that make sense?

If you don't wish to help me, please don't continue. It doesn't do any good when someone tries to ask respectful questions to be told on a forum for exactly that to go elsewhere to find answers.

Daviod
 

driscolldb

Aug 24, 2018
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You know what, forget it. I looked at a few forums and there always seemed to be a few guys that want to do nothing but jump in making assumptions and talking down to people.

I settled on this one because it seemed a little more receiving.

"Go look it up, there's a wealth of info out there" is less than nothing as far as help goes.

Anytime you come across any kind of question on this website you should say that "There's a wealth of info out there. You can google it". Do that for any and all things, and you'll quickly see how ridiculous a response it is. Especially on a forum dedicated to the very subject.

"You don't seem to appreciate.." is a massive assumption that could have been cleared up with some thoughtful questions.

You guys enjoy your forum. This forum apparently isn't part of the wealth of information on the net.

David
 
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Bluejets

Oct 5, 2014
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No one was telling you to go jump, simply that Whonoes was pointing out that the info you and many others require at times is already in many places on the net without have to go in to drawn out explanations all over again.
You must start any understanding of projects on a simple basis and advance from there, not jump in half way up a rather long ladder of knowledge and expect to become enlightened.
 

WHONOES

May 20, 2017
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I
No one was telling you to go jump, simply that Whonoes was pointing out that the info you and many others require at times is already in many places on the net without have to go in to drawn out explanations all over again.
You must start any understanding of projects on a simple basis and advance from there, not jump in half way up a rather long ladder of knowledge and expect to become enlightened.
Thanks "Bluejets" couldn't have put it better.
 

WHONOES

May 20, 2017
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You know what, forget it. I looked at a few forums and there always seemed to be a few guys that want to do nothing but jump in making assumptions and talking down to people.

I settled on this one because it seemed a little more receiving.

"Go look it up, there's a wealth of info out there" is less than nothing as far as help goes.

Anytime you come across any kind of question on this website you should say that "There's a wealth of info out there. You can google it". Do that for any and all things, and you'll quickly see how ridiculous a response it is. Especially on a forum dedicated to the very subject.

"You don't seem to appreciate.." is a massive assumption that could have been cleared up with some thoughtful questions.

You guys enjoy your forum. This forum apparently isn't part of the wealth of information on the net.

David
A confrontational attitude will not endear you to people that are trying to help.
 

Audioguru

Sep 24, 2016
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Driscolldb said that he wants to top up the charge on products that have a charger inside them and that charger is powered from USB 5V, not to charge batteries without using a proper charger circuit.

I assume his solar panel produces 18.2V when it is fully loaded at 5.49V. Then when it has a low load current its output voltage will be 25V or more.

Maybe Driscolldb does not understand that a 7805 voltage regulator with a 1A load gets extremely hot when it heats with (25V - 5V) x 1A= 20W. When the input to the 7805 is only 8V then it works fine and with an output current of 1A heats with only 3W. So the solar panel voltage is too high for 7805 regulators.
 

debe

Oct 15, 2011
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The panel he is using is obviously 18.2V open circuit, which a lot are. You could use a heap of cigarette lighter type of 5V usb units, they are cheap & are switching type also handle 12V to 24 V dc input.
 

debe

Oct 15, 2011
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This is the specs on a 80W panel & the open circuit voltage is as high as it gets.PANEL.1.JPG PANEL.2.JPG
 

Audioguru

Sep 24, 2016
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I have a solar panel made to trickle charge a car battery. Its current is rated at 13.2V and its open circuit voltage at noon in summer is 18V.
His solar panel higher voltage might power a battery charger circuit.
 

Audioguru

Sep 24, 2016
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The panel he is using is obviously 18.2V open circuit, which a lot are. You could use a heap of cigarette lighter type of 5V usb units, they are cheap & are switching type also handle 12V to 24 V dc input.
I found a box full of some cheap cigarette lighter type of 5V USB units thrown away. I took one to see what the Chinese people put in them but it was all burnt inside. They are not reliable and might burn down your solar panel.
 

Externet

Aug 24, 2009
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It would be simple to use the panel output fed to a 5V DC duck converter and connect many USB jacks as needed. No need to cut or alter the panel risking it. Just a separate box housing the wiring, DC converter and jacks will yield only the panel wiring as input, and a bunch of jacks flush on the box.
Allows the panel to be by the window and distant from a charging/supply table. No need to implement cigarette jacks.
Adding a fuse to each and a LED to tell it is powered could be convenient. Some of the following pictures are wrong for DC-to-DC, but there is many available in the market.
upload_2018-9-1_9-33-58.png

755a8864-dae6-4b8b-adc3-7b88769021b3_1.61797d3547684f2493ec7656c36d8e52.jpeg
bc0fda1a-534e-4e54-85c3-468c9a3864b5_1.698621df1a047dd4ff0b818730a0accb.jpeg

91b2ed3b-b72d-4622-8353-f5e53e9fcd07_1.2d3286e9489c978160c1a5c2df22b660.jpeg


- Replace the inlet USB connector with the cable from the DC converter -
 
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