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Hampshire
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 Hello everyone, just got side tracked and I wanted to build a 'big' solar charger for my video camera that requires 2.1 amps at 5v.

I bought a solar panel from Maplin down Christchurch for 15 quid it was a 2.4w at 12v (works out to be about 0.2 Amp). My idea was for it to be converteed down to 5v so i can feed it in to a power bank i hope to buy from ebay.
http://www.ebay.co.uk/itm/10000mAh-External-Battery-Charger-Power-Bank-2-USB-For-Ipad-iPhone-4-4S-MID-HTC-/270939385624?pt=LH_DefaultDomain_3&hash=item3f153eef18

My initial idea was to put the 12v solar panel into a 5v regulator I know it wouldn't be efficient but it would charge...

In reality when I hooked it up to a multi-metre and I was receiving around 18v. Though so high i plugged it in to a low drop out regulator to see what I would get. I didn't get any voltage on the other side. I was wondering if any one had any ideas on what I could do do bring the 12-20v solar panel to a steady voltage regardless of current at the moment at 5v.


Thank you for reading Trevor Boultwood
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TrevorB

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Solar panels are rated by the battery voltage they should charge.  A "12V" panel will charge a 12V lead-acid accumulator even when cloudy.  Open circuit full-sunlight voltages are a lot higher than under load when cloudy voltages.  The panel has to drop voltage through the series diode and then provide 14V (fully charged 12V lead acid goes up to nearly 14V).

To get the most power out of it a maximum-power-point (MPP) tracking charge controller would be needed - these dynamically vary the amount of buck or boost in a DC-DC converter to keep the cell at its maximum power point.

If you are only interested in power in full sun then that panel probably should be operated around 15 to 16V.
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Hampshire
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Hello and thank you for the reply, after testing it under a load yes, it does go to 12/13 volts which I guess is a start. IS there now any way of changing that down to 5volts? Or could I charge the power bank with the 12v? IS that possible? Any thank looking forwards to the reply. smiley Trevor boultwood
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TrevorB

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A 7805  can cope with 35V input. Presumably you got 5V out with no load. If the camera expects to be able to draw 2A, (which seems a lot) then the solar panel isn't going to supply more than 200mA, so the output voltage will drop.
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Hampshire
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I didnt really mention it well, but the solar panel will hopefully regulated down to 5v for the power bank, (10000 mhA) and then that will charge many differant devices.
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Ah, sorry so solar charges battery, then battery charges other things. The battery bank expects 1A at 5V, if its charging a LiPo, then it probably does expect to have 1A available for its smart charging.

You could use a good old 12V lead acid battery charges from the solar and then a 7805 or higher power providing the 5V out to the camera etc.



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Hampshire
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I was very much deciding that! :L I could make a small bag sewed around it and stuff and it would provide I huge amount of power!, I was also thinking, using the solar panel to charge a small 12v battery like the size of a D shape, and then use that, I know it would only have like 2000mAh but I guess it would do the trick nicely! :L So I guess I just need to find a smallish 12v battery! Or I could of lead! I have a look around, thank you muchly for the inspiration! and thanks to all the others! smiley-grin
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