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how should i be making an USB solar charger? Answered

i have a 12V solar panel lying around, and want to make an USB charger with it.
i've looked around, but i cant find anything with the same specs as i have...

anyway, i want something that i can put indoors overday, that charges something (batteries?) and then that something charges my MP3 player overnight.
what is the best way/instructable to use?

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Re-design

Best Answer 8 years ago

I've never seen one.

You could change several 9 volt batteries in parallel then switch and have them charge your usb thingie.  You'll need to use a voltage regulator to get the 12 v's down to 10 to charge the batteries.  THen another voltage regulator to get the 9 v's down to 5 for the use.

You can use a dpdt on off on switch to do the change over.  The center is off with battery charge on one side and usb charge on the other.

It's a lot of work just to charge something that you can charge in an hour just by plugging into your computer but it's good experience and there's not a better way to learn electronics than designing and building something.

You can get voltage regulator info by googeling it and the pinout for the usb port also.

Good luck.

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godofalRe-design

Answer 8 years ago

its also for becouse its better, and partly becouse i have to much spare time :D
but ur saying i need 10V to charge 9V batteries?

anyway, is it safe to charge rechargable batteries straight off a solar panel? (no li-ion ofcourse)

if so, il just place enough AA's for 12V, charge those off the panel and then just use a 5V regulator and a switch for charging my MP3 player...

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godofalgodofal

Answer 8 years ago

oh, and in case u wanted 2 ask, yes im going to documentate and make an instructable out of it if it works out ok :)

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Re-designgodofal

Answer 8 years ago

Unless it's a large panel it's only going to slow charge so it shouldn't be a problem.

And you do need a little higher voltage than you're charging since you loose some in the charging due to restances.

Documenting it for instructables is an understood.

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godofalRe-design

Answer 8 years ago

but its not a problem to charge 8 batteries(1.5V) in series with 12 V?

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Re-designgodofal

Answer 8 years ago

I don't think 12 v. would get 8 batteries to full voltage.  But some 1.5 v. rechargeables are only 1.2 volts.

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godofalgodofal

Answer 8 years ago

just found some 1.2V AA's, so i can use 8 of them and then it charges OK?