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Page:Popular Science Monthly Volume 90.djvu/964

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948

��Popular Science Monthly

��very fast for making these holes. The three-series eight-parallel battery shown in Hg. 2 requires i6 of the U-shaped pieces and also i6 pieces of the short L-shaped length.

The filling for the lead tubes is made up of a thick mixture of red lead and dilute

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���This diagram shows the ar- rangement of the cells and lead fillers for use where the battery is to be charged with a current from other batteries

��sulphuric acid — one part acid to two parts water. Be careful in making the dilute solution of acid. Always pour a small quantity of the acid in the water and stir vigorously. Never add water to the acid. The paste mixture should be about as thick as putty. As there must be different mixtures in each leg of the lead tube the other mixture is made up in the same manner except that yellow lead — litharge — is used instead of the red lead. One leg of each tube is stuffed full of the red lead mixture and its mate with the yellow. All of the double elements are treated in a like manner. In making up the smaller lengths fill half their number with the red lead and the other half with the yel- low; thus for the 24-series unit there will be two of the short tubes used — one filled with and the other with yellow lead. 3-series, 8-parallel unit there will be 8 short pieces filled with red lead and 8 with the yellow lead. In either case force the paste in so that it will be pushed out through the

��holes, then scrape ofT the excess so that it presents a smooth surface.

Before the elements are assembled they must be treated for charging. One method is to charge the assembled battery and then discharge in the opposite direction. This operation should be repeated four or five times. Another way is to lay the legs filled with the red lead in a strong solution of chloiide of lime, or a solution of nitric acid, or sulphuric acid — one part acid to two parts water. Allow the elements to remain in the solution until they are some- what roughened.

If the latter method is used the battery is ready to assemble. This is very plainly shown in the illustrations. In building up the battery shown in Fig. 2 a single red lead element is placed in the end test tube and one leg of a yellow lead double element is introduced into the same test tube, the other leg being placed in the second tube. Continue by using one more double element and finish with a single yellow lead element. This makes each tube with one positive element and one negative, and one unit of three cells is complete in the series. The other 7 units are built up in the same manner. The illustration Fig. i shows plainly how the 24-cell unit is made up, starting with a single element and finishing with the opposite single element, the inter- mediate ones being filled with the double elements.

Two binding posts are used on the 24-celI, as shown. The screws are passed through the frame and through a hole in the end of the element. This is plainly shown in

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��FOR 3-CELL UNIT MAKL 16

��fORE4-CELLUNI7 MANE 2

BEND IN THIS- MANNER

FOR 3-CELL UNIT MAKE 16

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��DRILL FOR BINDING POST

��The elements are made of lead pipe cut to the right lengths, bent into shape for entering the cells and drilled for holes. Each tube has one positive and one negative element

��red lead For the

��B, Fig. I. For the 3-series, 8-parallel unit there are required 16 binding posts, two for each unit.. The posts are fastened in the same manner as for the 24-cell unit. The reason 16 posts are needed is that the cells must be connected in parallel for charging

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