For our research in solar electric charging, we started off with testing four solar panel setups to obtain their current-voltage (IV) characteristic curves and determine if each one was capable of charging a phone. Each individual panel used in these setups were rated at 3 W and 6 V. The expected ratings for each setup are the theoretical values assuming the manufacturer ratings mentioned above are accurate.
To link these panels together, a simple soldering job was done. The panels had the positive and negative leads clearly labeled, so getting the various arrangements was incredibly straightforward.
Two Panels in Series:
Expected rating: 12 V and 0.5 A
We were unable to attain the IV curve with the cell phone charging because the panels were reaching temperatures above 50°C too quickly. At these temperatures, the panels outputted so low current that the phone could not charge with.
However, we were still able to get the IV curve for the panel alone to determine a maximum power point of 11.5 V at 3 A.
Two Panels in Parallel:
Expected rating: 6 V and 1 A
This setup showed the best data out of the four we tested. The curves behaved exactly how we predicted them to, and the maximum power point was easily obtained.
Three Panels in Parallel:
Expected rating: 6 V and 1.5 A
For this setup, we could not fit a model to the data for the IV curve of the panel when charging our phone. However, the phone load line behaved just as it should and was able to charge with 4.41 V at 0.33 A.
Expected rating: 12 V and 1 A
This setup produced a very interesting pattern in the data when we tried to charge our phone with it. The IV curve for the setup alone behaved as it should. But, when charging the phone, the curve dropped when the ideal voltage was reached and then returned to normal after the phone stopped charging at high voltages.