Making some custom solar panels
Grabbing some sunlight
Bare solar cells are brittle, hard to make reliable connections to,only output 0.5V and need a cover to protect them if used outdoors.
I picked up some cute solar cells that were designed to be used in outdoor solar powered night lights. They are actually a complete solar panel. They will output 4.7V with no load, and at their max current of ~85MA, the voltage is about 3.2V.
The cells have plated copper flat wire terminals, and are pretty rugged. A guy in Foxboro MA is selling them on e-bay right now.
I found that 4 cells in series will start and run two small 50ma@12V fans.
Made an air cooled garden hat for Sue.
Next I wanted to run a 4" 12V fan , so I took a 1/8" thick piece of PVC sheet and glued 8 of the cells to it with silicone calk. This panel puts out 165ma and develops ~8V across the 250MA fan, which runs it nicely, but not at full power.
I then made a new panel for my solar power demo hat, which has 3 4" fans. The panel will not run the fans alone, but will charge the NIMH 1100MAH AA cells that are embedded into the hat. The panel outputs ~400MA and will allow several hours of runtime.
The final panel is a reconfigurable output 22.5 Watt panel. Each string of 7 cells outputs 32V OC @ 85ma, and is terminated at the terminal area.
The available configurations:
256V @ 85mA
The price of ~$4.12/Watt is not cheap compared to larger ready made panels, but the voltage range of 3.2 to 4.5V allows a single cell to power a pic microcontroller, and the ease of use and mounting allow custom panels to be made in any configuration you like.
Next project is to connect the 256V panel to the Insight HV pack for parking lot topping off and re balancing of the battery charge.
More on this project :
Plugging into the sun blog
When putting series strings of cells in parallel with other series strings, each string should have a diode to assure that back conduction does not take place.