A few years ago I was living off the power grid with some friends and we went to the scrap yard looking for some deep cycle batteries. Ended up getting some huge nicad forklift batteries for free. Turned out we couldn't use them for power but uon disassembleing them discovered that they had stacks of dense perforated nickel coated steel plates all bolted together and spaced just about an 1/8" apart. Plates were about 8"x12"