Solar iPhone charger

Community Projects
1

Hi,

I’m trying to build a small system for charging my cell phone with a solar panel. This includes:

  1. Solar cell (5 W in full sunlight, it’s a CIGS cell)

  2. A Sparkfun Solar Buddy charger

  3. 2000 mAhr 3.7V Li-ion battery

  4. TK0445 DC-DC 3V to 5V buck/boost converter with a USB female jack

Before trying to charge with the solar cell, I fully charged the Li-ion battery and plugged it into the Solar Buddy. On the LOAD terminals, I measure a voltage of 3.79 V, so I know that’s working. I connect two leads to the LOAD terminals to my DC-DC converter, which converts the voltage to 5.2 V. With a multimeter, I read 5.2 V across the USB terminals that correspond to +5V and ground. Then I plug in my iPhone 5 USB cable, and at the end of those leads I also read 5.2 V.

One would think that plugging my iPhone in, it would start charging. However, it’s not charging. Is the 5.2V too high? Am I missing another component in this circuit?

Thank you for your help!

2

Some, if not all, Apple products require certain voltages to be present on the USB data lines in order to charge. Google will point you toward the details, but Adafruit has a tutorial somewhere.