i've been using distilled water, though its probably not pure, but the resistance is probably still high, it measures about 1500 ohms across the cell, actual accuracy of that reading is unknown, i can go up to about 4 amps then i back off, trying not to over heat anything, and also we should never need more than 5 amps, that was the max of his system, and 3.3 amps in the other system, i also notice a drop in the rectified voltage, 125 volts when the dial is at 140
this is the opto circuit:
(http://img.photobucket.com/albums/v81/bigbuba/Picture2-3.png)