# Increase Amperage

Discussion in 'General Electronics Chat' started by Alex5776, May 15, 2011.

1. ### Alex5776 Thread Starter New Member

May 15, 2011
2
0
Hi
I have a solar panel, small one, that is generating about 22 volts and only like 0.03 Amps. I want it to be able to charge my iPhone. Is there a way to decrease the volts and increase amps

iPhone requires 5 Volts, and 1.1 Amps.

I know that is a big step up but somebody has got to know a way.

-Alex

Apr 5, 2008
15,806
2,390
Hello,

The wanted current at the output can not be reached.
The input power is 22 X 0.03 = 0.66 Watt.
The output current can be 0.66 / 5 = 0.132 A, when there are no losses in the stepdown converter.

Bertus

Dec 26, 2010
2,147
300
A practical converter would of course have losses, so the actual current available would be a bit less than 132mA.

85% efficiency would not be unreasonable so you might get about 110mA, or one tenth of what you actually want.

If you really need 1.1A at 5V, you are going to need a very much bigger panel, especially if you want it to work other than in full noon-day sunlight.

4. ### Alex5776 Thread Starter New Member

May 15, 2011
2
0
Thank you so much, I thought is was a huge step.
Now I get to go shopping! For a bigger or at least better panel!

5. ### Jaguarjoe Active Member

Apr 7, 2010
770
90
A solar panel delivers max voltage when it is open circuited so current is 0 and power is 0. It develops max current when short circuited so voltage is 0 and power is 0 once again. Somewhere between the two it develops maximum power.
If you need 5v @ 1.1a @ 85% eff, you'll need at least 6.5 watts from the panel.

6. ### K7GUH Member

Jan 28, 2011
191
23
Read your paperwork carefully. Your iPhone may require 5.5 volts at 1 amp to operate, not to charge the battery. The battery charging requirement could reasonably be less than 1 amp. If you get a larger solar panel, be sure to get also a voltage regulator for the recommended charging voltage for the iPhone, otherwise you will almost certainly ruin the battery within a few days.