MINIATURE LAMP burns for about a minute as this simple storage battery discharges.

By Carleton J. Lynde, Ph. D.Professor Emeritus of Physics, Columbia University

YOU can easily make a small storagebattery that will light a 1-1/2-volt

lamp, ring a bell or run a toy motor—and you can do it with safe, easy-to-find,inexpensive materials. All that's re-quired is a small amount of sheet lead,a few tacks, a strip of wood, a shortlength of wire, two dry cells and atumbler or beaker of water.

Your first step is to cut the sheet leadinto two 4xl-1/2-inch strips. Then take a4xlx1/2-inch strip of wood and tack thelead strips on opposite sides as shown inone of the photographs. Put one tack ineach side first. The second tack on eachside is used as a terminal for a nine-inch length of wire, so wrap the end ofthe wire under the head of the tack be-fore you drive it in. Next dissolve aheaping tablespoonf ul of baking soda ina tumbler of hot water and lay thewooden strip across the top so that thelead strips are in the solution.

To charge your battery, you must

connect the two nine-inch wires for fiveminutes to two 1-1/2-volt dry cells joinedin series. The last photograph showshow the wires are connected to accom-plish this. When the five minutes are up,disconnect the wires from the dry cellsand connect them to the terminals of alight, bell or toy motor. Your storagebattery will operate any of them forabout a minute.

Here is what happens: Originally,each strip of lead has a gray coating oflead oxide (PbO) which is formed natu-rally from contact with the air. Whenthe strips are connected to the batteries,one is connected to a plus terminal andthe other is connected to a negativeterminal; thus one is a positive strip andthe other is a negative strip. The directcurrent from the batteries causes oxy-gen to be deposited on the positive stripand hydrogen to be deposited on thenegative strip. The hydrogen combineswith the oxygen on the negative strip

106 Mechanix Illustrated

and takes it away, leaving lead (Pb).The oxygen combines with the oxy-gen on the positive strip and stays,making it lead peroxide (PbO,).Therefore, one strip is lead and theother is lead peroxide and your stor-age battery is fully charged.

When you disconnect the wiresfrom the dry cells and connect themto a lamp, bell or motor, your storagebattery starts to discharge and thedirection of the current, or the flow ofthe hydrogen and oxygen, is re-versed. Then the hydrogen causes thelead peroxide (PbO2) to change tolead oxide (PbO) and the oxygenchanges the lead (Pb) to lead oxide(PbO). Thus both strips are onceagain lead oxide and your storagebattery is fully discharged. You canrepeat the process by recharging thestorage battery with the dry cells.Naturally, with larger plates, you candraw more current. •

SHEET LEAD is cut into strips. It has anaturally acquired coating of lead oxide.

TACKS secure strips of lead to wood. Awire extends from one tack on each side.

BAKING SODA is dissolved in a beakerof hot water before immersing the lead.

CHARGE the battery by connecting thewires to two dry cells wired in series.

July, 1959 107