Old pieces of Oroko and Beech.
Mod maker 510.and bottle.
Fogstar battery.
Cut some old copper pipe to make contacts.
Hand sawn box is a bit rough.
But it works quite well.
I made them by cutting some old copper pipe. Flatten in a small vise( hammer will do).
Then cut with tin snips drill 12 mill hole and fit to suit. Total cost to make was 12quid.Plus battery plus tank.