Thank you for posting about the edison battery. Due to the drawbacks
listed, I think the search for optimum material selection is still open.
My copy of General Chemistry by Pauling still shows the widest
Voltages between Ca (2.
, Mg, (2.35), Al (1.75) Zn(.90), Fe (.50), Sn-Pb
(.20) & Cu (-.30) these figures being approximates. They're also the cheapest and most available. Lets remember that a cell needn't be perfect
in all respects to achieve our objectives, but only "good enough." I still feel
ant_davison's kettle coils to be most compact. With unions at the bottom
and disimilar metals in each side, SS coil plates, maybe POH in lieu of
acid, we could line the U's up in rows or clusters of cells. Using 4" PVC
pipe, a battery with 7 cells would only be 12" in dia. The right selection of
materials should give us a battery of roughly 12V, easy enough to overcharge.