usb 2.0 solar charger

[calisto]

hi guys i found this forum in a search, looked like a great place to ask for some help. I'm having a problem with my solar usb charger; I have a blinking charging signal but the battery is draining. I am using this only for my smartphone by the way. I'm in FL so there is lots of sun beam on it.

here's the setup. I am stumped, tried a few things and failed. Do I have to work strictly with copper wire? because most of these are wires pulled from a computer power supply unit.

http://imageshack.us/photo/my-images/210/panelspec.jpg/ (Panel specs)

http://imageshack.us/photo/my-images/837/55464057.jpg/ (Diagram)

http://imageshack.us/photo/my-images/254/batut.jpg/ (My smartphone battery)


thanks!

 

[CocaCola]

I have a blinking charging signal but the battery is draining.

This indicates that the circuit is 'helping' charge the phone but the phones drain rate is in excess of the charge rate... And that is not hard to imagine since the solar panel is rated at 5W and most new phones have a charge rate in excess of 1A @ 5V aka 5 Watts... Even at full capacity no loss the solar panel simply can't provide enough juice to charge properly or at least efficiently... You are basically slow charging the phone and if you are using the phone at the same time it's almost certainly draining the battery faster than the slow charge...

It might help if you get rid of the linear regulator and use a small switching one to get more efficiency, but even then you are splitting hairs if you are already having issues and based on the 5W output...

Time for a bigger higher output solar panel if you want this to work, or possibly 2 to 4 of the ones you have...

 

[calisto]

Thanks for your reply. its a dual-core processor phone with 4g always on. I thought it would be the same as a wall plug no matter how much strain. Also with zero usage the battery is still draining, phone turned on. I will drain the battery tonight and first thing in the morning I can verify if the phone is actually receiving a charge at all. Some people have told me to put a diode in but im not sure how to and what it does. Oh yeah and work on finding a larger solar panel but they're extremely expensive,

edit to add: im a newbie to everything soldering and electronics, it is very interesting and i want to learn more. Im going off videos tutorials which dont show much or give great information. I'm only just beginning to get the gist of soldering.

 

[calisto]

Okay guys, The battery indicator on my phone reads from 1 - 100. It was at 10 when I connected it to the solar panel, i checked it an hour later, turned it the phone on and it read a 7, What am i going to do? I'm just about to give up.

 

[CocaCola]

OWhat am i going to do? I'm just about to give up.

I already explained your problem and what to do, re-read my previous post you might not like to hear what I said but regardless it's almost certainly the issue...

 

[calisto]

i dont think you understand the problem but thank you anyway, ill try another forum

 

[(*steve*)]

Sure. If you don't like the answers, look for different ones elsewhere.

You will get an absolute maximum of 320 mA charge current, and only when the panel is normal to the sun and there is no cloud or haze.

It is possible that the phone wants to draw more than this, loads down the voltage and gives up. It is actually possible that almost zero charging is taking place.

I would recommend you get one of the cigarette lighter to USB converters and power that from your solar panel. If the device is one of the new (very small) switchmode ones you will get more current and it *might* work.

Depending on the phone, you may need to do some magic to tell it that the charger is only capable of 500mA so it doesn't cause the voltage to drop below 5V too often.

p.s. yes you need to use copper wires (the wires you pulled from the PSU are copper)

a diode prevents the phone from discharging back through the solar panel at night. if you measure the current with the solar panel in darkness (place it face down on a surface) and it reverses, then you need a diode. If it simply falls to zero, you're OK without one.

 

[CocaCola]

i dont think you understand the problem but thank you anyway, ill try another forum

I understand the problem fully, just because the answer is not what you want to hear or you choose to ignore what I said, doesn't equate to me not knowing the issue... Do you understand Wattage, and loss when converting? Do you understand that just because a solar panel can produce 5W in a lab under perfect direct light controlled circumstances doesn't mean it actually does in the real world?

The problem is simple, the phones ambient drain exceeds the charging capacity of the solar cell as you have it hooked up and designed, it's really that simple...

You need to increase the capacity of the solar cell so that it's charge power exceeds the power drain of the phone, until you accept this as fact and address that problem you will get nowhere...

 

[QuantumCheese]

Lets try putting it like this.
The voltage out of the panel, when used at it's maximum efficiency point is 16.8V
In full-on direct sunlight you will get 16.8V @ 0.3A that = 5.04W

Your using a Linear regulator. In simple terms that takes in 16.8V and puts out 5V,
so now your looking at a maximum output of 5x0.3 = 1.5W.
The rest of the panels output 11.8V is turned into heat now that's 11.8V x 0.3A = 3.54W, so in a nutshell your throwing away twice as much power in heat as will end up coming out of the USB connector. (where else would the extra volts go? a 7805 is no magician)

The only way to get anything usable out of solar is, to do as CC suggested & use a 'switcher', but the main thing to remember is "Solar Panels give their rated output in full sunlight, if you can't feel the heat of the suns rays, neither can they"
In the sahara this circuit might work!