Typically each anode 39 may be 0.1 to 0.15 inches (0.25-0.38 cm.) thick and have an area of 120-145 in.2 (780-930 cm.2), for a total of about 60 lbs. (30 kg.) per a 72 v. set of air cell batteries B. It will be understood that six 12 v. batteries B may be used rather than three 24 v. ones, as illustrated, or that other voltage levels such as 24 v. or 60 v. may be utilized, simply by series and par