test results of rollable panel

Skyko Solar Expert Posts: 121 ✭✭✭✭✭
Hi guys,

I posted this over in the Nexus One forum but figured it might link in with the solar charging we discuss here.

I just performed a few simple tests using my new Powerfilm 14 watt rollable panel. In the wimpy Seattle morning sun I measured over 10.6 watts into a 25 ohm load and I charged up about 8% of my N1 battery in around 10 minutes using a Belkin 12-24V input 5V 700mA max usb output car cig. lighter dc-dc converter. I am extremely impressed with this panel, both in the output and the quality (even the electrical connectors have marine grade rubber seals to keep out moisture). I also really like the Nexus One that arrived yesterday

I may add a circuit on the front end of the dc-dc converter to cut off input power if the panel voltage droops below a certain amount. This would probably be just a simple comparator with zener diode reference driving a low Rds_on N channel mosfet. I noticed in my tests with a dummy load that if you are drawing 500mA from the car adapter usb port and the input voltage from the solar panel falls below about 8.5V then the output voltage starts to drop below 5V. I don't know what this would do to the N1...it may just ignore low voltage charging power or it may drain the battery of the N1 or even damage it. If I use this circuit to cut power to the charger if the panel is shaded and producing low output then things might be safest.

Anyway, here are the pics of the panel powering a 25ohm load (the Fluke 189 is measuring 16.3 volts across the 25 ohm load, which is about 10.6 watts).