I made one of those large batteries today using a carbon water filter element and it worked extremely well. It put out 1.75 volts and drove a load at 21mA.
I have it hooked up to the original Earth Light circuit that I built yesterday. Felt was used as the insulator and only distilled water was applied. I will put it in a shallow dish with distilled water and see just how long it will run. I will also take temperature readings ( I got a small infrared temp meter at Radio Shack today) to see what happen there.
@ John B.
I don't understand the new circuit. I can build it but I need a little more help. Thanks
Here is a video of the BIG battery that I made:
YouTube - Bedini Earth Light with BIG battery.ASF