i need help with a simple home project

[voultsi]

Hello, fisrt of all this is my first post. I know it is going to sound like a dumb question i am really newbie and i made a solar usb phone charger. It consists of a solar panel (3v) that charges two 1.5 v nimh rechargable batteries that charge the phone.My problem is that when i plug my phone to it so it can charge, it indicates charging but it doesnt, it just stays the same.Firstly , what could be the problem and secondly if i put one more solar panel(the same ) and one more battery to be charged , will it charge my phone? Also , how can i check how many amps one solar panel provides and how many a phone needs, is there any danger if the panels output more amps?( NO , i dont have any info from the manufacturer about the panels)

 

[betwixt]

Quite possibly your phone isn't telling you the truth. When it says it is charging it probably really means it has detected voltage across the USB power inputs rather than power is actually being stored in the batteries. It is imposible to be concusive without knowing the charge characteristics and the PV panel output under load.

I would think the problem is you don't have enough voltage to start with. The PV is probably inadequate for the job. As a rough guide, you need about 1A to charge a phone if the battery is flat so you would need at least 3.3W of PV output and more likely 5 - 6 W. It is difficult to advise what size panel that would equate to but a guess would be 120cm2 or so.

More amps = better, the batteries will only draw what they need, any extra won't be used.

Brian.

 

[Audioguru]

Most cell phones use a Lithium battery that is 3.2V when dead and is 4.2V when fully charged. The charging circuit inside the phone is designed for a 5V input. So it cannot be charged from two 1.5V Ni-MH cells in series.

Maybe you are talking about a wireless home phone? Mine came with a very cheap Chinese Ni-Cad battery with three cells and it is 3.6V. Its AC adapter is rated at 6VDC.