charging circuit help

Thread Starter


Joined Dec 21, 2011
I would like to build a simple charging circuit where I can collect light using solar panels (small panels) and store the energy. I would then like to measure the amount of energy collected. I was thinking of hooking up the panels to a capacitor and measuring the voltage at various points in time to see how much energy has been collected. Is it that simple or is there more to it?


Joined Oct 26, 2011
As an experiment, this is possible--only use a very small PV panel and a very large capacitor so that it does not charge so quickly that you cannot obtain measurements. Set it up for a charge time of about 10 minutes.

Remember the useful relationship: IT = CV
I = current in amps (constant current)
T = elapsed time in seconds
C = capacitance in farads
V = volts

Plot Voltage and current vs time on an Excel Spreadsheet Graph

ε = CV²/2

Plot energy vs time

Plot relative efficiency vs output voltage

Answer the questions:
Why does the energy increase exponentially with time?
How can this happen with a relatively constant current out of the PV panel?
Why does the efficiency change with output voltage?