iphone solar charger (again)

Have read through alot of topics but cant find my question answered...

If i use 5v solar panels, with lets say 1000mA  power, and simply solder wires from panels to a female usb connector

ex. if i buy a usb extension (male one end /female other end) and cut away the male part and solder the other female part to panels

would this simple circuit charge a iphone ,,or would there have to be other electronic parts involved to make charging happen?

If this does not work , im thinking of buying a car usb socket and solder to 12-15v panels ,   that should be bombproof as long as you now that the specific socket works with iphone right ?

Downside of that , as i read somewhere on the net is that you loose power when transforming current down from 12 to 5v ?

is that right

ok hope someone has got a answer to me 


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kristerh (author) 3 years ago
Hi ,
Im back after having some probs with loggin in,forgot password and had typed email wrong,

anyway,thanks for your answers so far,

i ve ordered both 5v panels and 15v panels ,

if the 5v wouldn't work

15 v panels should be 100% sure to work together with a car 12->24v input usb socket charger

so we'll se when i receive the items how it works out!

meanwhile , two questions bothers me abit ,

first: the diodes i bought : are they the right type and how many to use?

schottky 15A 45v are the rating


as i will use 5 panels in parallel , should there be one diode for each panel or is it enough to use one for the complete circuit


as the 15v panels are rated 150ma that only adds to 750ma total, but the wattage would be pretty high 11,25w total,

how would that come out after the car charger socket that is rated 1A , will i get 1A out or only 750ma? are all that wattage wasted enegy? or will the 12v usb car socket transform that 15v 11w excess power in some magic way

As you maybe could guess from my questions , i have very limited knowledge in how electricity works , so laugh all you want ,but please serious answeres

regards krister
There is a power loss with any circuitry very little is 100% efficient.

5 volts 1000 ma should charge the phone does the solar panel have a built in diode?

klee27x3 years ago
Some chargers need a short between the data lines on the USB connector. And some apple devices need to see a specific voltage. A couple of resistors have to be placed on the data lines. I can't recall the specifics. Should be easy to google.

Of those two options, the first option is way better. Using a 5V 1000mA output solar panel would work fine, but I would be sure to check the voltage first. Of course, it will cut in and out when it gets cloudy, but this would not harm your phone. As long as voltage doesn't spike too high. Anything under 5.5V would probably be fine.

If I were doing this, I might use a small battery on the output of the solar panel to act as a buffer. 4 NiCd batteries in series should work. This would keep the output steady, even if the panel were moved or put in the shade. 4 NiCd batteries in series would charge fine from the panel, and the output would be up to 4.8V when the sun goes down. USB charger specification allow for voltage drop all the way down to 4.4V under load, FYI.
klee27x klee27x3 years ago
Detail: with the small battery buffer on there, your charger wouldn't work unless/until the voltage on the buffer battery reached at least ~4.4V. The battery effectively anchors the output of the solar panel to w/e the voltage on the batter is at, which is fairly linearly related to state of charge on NiCd chemistry.

But once your buffer battery is charged up, you get smooth, uninterrupted output from the solar panel.

Re 12V panel: If you use a 12V panel, you will need approximately 2.4 times as much surface area to get the same amperage. The only plus side is that voltage dips down to 6-7V will not interrupt the output. But with a battery buffer on a 5V panel, I think you will get better efficiency, overall. I could be wrong.
Assuming you can find a solar panel that can offer 5V with at least 500mA under a load, yes. But your better off with a 12V panel (often they offer as much as 15V under full sun and no load) and a 5V regulator. Really no downside since your getting the power from the sun to start with. The 12V panel may be able to offer more amperage and your USB car socket is going to limit the output to between 500mA and 1A anyway.