Hi I'm trying to charge a capacitor to 5V from a small solar cell that only puts out 1.4V. Can this be done? It's a 2.2F capacitor and the cell puts out 20mA in decent sunlight. Can this be done easily? Do I need a boost circuit? If so, what's the best way to do this? Thanks
The capacitor energy at 5V is ½CV² = 27.5 Joules
The power from the solar panel is 20 mA * 1.4V = 28mW or 28mJ/s.
The time to charge for 100% efficiency is 27.5/28e-3 = 982 seconds or 16.4 minutes. Even at only 10% charging efficiency it would still be less than 3 hours.