Hi,
Here is a working DC resonant charging circuit.
The voltage across the Waterfuelcell is al least twice of the input voltage.
In my case almost 30Vpp against a 10v input.
You might pull the conclusion that the waterfuelcell acts like a small battery or capacitor.
Tune the circuit till you reach the highest voltage across the waterfuelcell.
USE ONLY TABWATER OR DESTILLED. NO CHEMICALS ALLOWED IN HERE.
Type of diode: Not important. Only heavy enough for the amps you use
Type of coil: in my case 25 winding of 1mm wire on a metal lamel core. 1mH
Just play with some cores you have.
Type of FET: Not important. Any N type will do. The lower the internal resistance the better. Your choice depends on voltage and amps.
Frequency: try to stay above 1khz with tuning. My test was done around 10khz.
Steve
http://www.tpub.com/content/armymunitions/mm50058/mm500580088.htmhttp://www.richieburnett.co.uk/dcreschg.html#resonanthttp://teslahv.com/DC%20Resonant.htm