Need help in a simple Solar Cell charger!
 

Hi everyone,

First of all, I'm not specialist in the field of electricity but I love it so much. Any way, I decided to make a simple solar charger for my phone battery. All I got till now is that I should use simple cell, regulator, current limiter, charge controller and some capacitors for the regulator.

The battery needs 5V DC and 500:900 mA to be well-charged so I decided to use a simple solar cell of maybe 6-7 volts output. You know that voltage and ampere vary according to light intensity from the sun and the battery needs constant gains so I used an LM7805 voltage regulator that supplies constant +5V DC and up to 1A; this about the voltage. And concerning the current, the 1A of the regulator should be decreased to the required rate, i.e, to 500:900 mA through the current limiter.


So, I don't know how to start or how the circuit will be :confused:


All I know is the regulator circuit as shown

http://freedatasheets.com/blog/uploa...eet-730098.gif


Thus, I need your help in how the full circuit will be
I mean " Solar cell, voltage regulator, current limiter, charger controller(that protect the battery from over-charging).... is there anything else I don't know??


Please if you know anything, don't hesitate to share me your knowledge :)

Regards,

Khaled

No, you got it. You are actually powering the charger circuit in your cell phone not directly charging the battery. So the idea is to limit the voltage to 5 volts so it doesn't damage the charging circuitry.

The regulator needs 7 volts in to work properly. That means the 7805 will have to handle 2 watts of heat. Even a small heatsink will do this. If you are careful you can solder the capacitors directly to the chip. That is a basic breadboard test method.

You mean that i don't need the charge controller? its already controlled by phone circuit?


So, you think what cell should I use to achieve this keeping in mind that this cell voltage is continuously changing. I know it's a small logarithmic change but still it's a change !

In this case, the Ampere is 1A. You think it's pretty good for the phone battery?.. You know, I got many electrical socket chargers and found their current outputs varying from 500:900 mA depending on the phone brand (Nokia, Samsung, etc).

Do I need a current limiter?


Please, let me know how to provide this heatsink? you know, I'm not specialist in electronics :D my major is Petroleum Engineering :)


Thanks a lot for your reply and help

My regards

any other replies??

6 or 7 volts is very borderline for the 5V regulator. I would use solar cells rated for about 9-12 volts for some safety margin. Photovoltaic cells are actually considered constant-current sources, BTW.
The charge control is built into the phone, so you only need to provide the proper voltage. An LM7805 in a TO220 package will handle this nicely. Any heat sink of a couple centimeters square should work to keep the chip cool enough.

The problem is any drop-out in voltage will appear as heat, this is in fact awful thing. But anyway, I'll find the suitable cell to use.

Awful... maybe. Unavoidable... most definitely.
You could use an LDO vreg like the TPS76850. Keep a mind of solar cell "in full sun" ratings.

Hi,
Here it is a link to Linear Technology read top page 19. It look like this is what are you looking.

Link to Linear Technology:http://cds.linear.com/docs/Datasheet/3108fb.pdf

I think this type is great, I'll try to change mind :D

Thanks for your link :)