At a supply-house obtain some sheets of cellulous fibre, three-sixteenths of an inch thick, or some asbestos cloth. If neither can be had, then soak some pieces of ordinary brown card-board in a solution of silicate of soda and let them dry. Lay a negative (yellow) plate on the table with the lug at the left ([Fig. 13] C). On this place a square of the fibre, asbestos, or card-board; and on top of it lay a positive (red) plate with the lug at the right side. Continue in this manner until the seven plates are stacked, the four negative lugs being at the left and the three positives at the right. Tie the plates securely together with cotton string bound about them in both directions; then stand the pile up so that the lugs are at the top, as shown at [Fig. 15], with every alternate lug in an opposite direction. Obtain two lead bars three-eighths of an inch square, or cut strips from the sheet-lead and solder them together, turning the ends as shown at [Fig. 13] D. Drop one of these bars into the lugs of the positive plates, as shown in [Fig. 15] H, and solder it fast at the three unions. Repeat this with the other bar in the lugs of the negative plates, and the pile will then be ready for immersion in the electrolyte. To both ends of each plate-bar solder binding-posts, so that the conductor-wires can be attached at one end and the feed-wires at the other. If a hard rubber or glass cell can be had for the battery so much the better; if not, a stout box may be made from pine, white-wood, or cypress, and thoroughly coated with asphaltum varnish or asphaltick. At an electrical supply-house you can purchase some “P and B” compound, which is acid and water proof. This is excellent for the inside coating as well as for the outside of the box.
The box should be made of wood not less than three-quarters of an inch thick, and the sides, ends, and bottom should be in one piece, free from knots, sappy places, or cracks. Brass screws should be used to hold the boards together, and before the joints are made the butt-ends of wood and the sides, against which they impinge, must be thoroughly coated with the asphaltum or compound. Put together the four sides first and then make the bottom fast, placing the screws two inches apart and countersinking the wood, so that the screw-heads will lie flush, as shown in [Fig. 16]. The box should be large enough to allow about one inch of space all around the pile, and deep enough for the solution to cover the plates and two inches of space above it to the top edge of the cell. The complete storage-battery will then appear as shown in [Fig. 17].
The electrolyte is composed of sulphuric acid and water in the proportion of one ounce of acid to four of water, making a five-part solution. This should be mixed in an earthen or glass jar, and the acid poured slowly into the water, the latter being stirred while the acid is added. When the solution cools (for adding acid to water creates heat), add about two ounces of bicarbonate of soda, and mix the solution thoroughly.
When the pile is in place within the box (having first removed the string which bound the plates together) pour the electrolyte slowly into the cell, taking care that none of it spatters, for it will eat clothing or anything else that it touches. Before placing the pile, or electrolyte, in the box, it should be thoroughly tested for leaks by allowing water to stand in it for several days. Indeed, you should be very generous with the asphaltum, or compound, when coating the angles and points inside the box; for if the acid solution gets at the screws it will corrode them and the box will soon leak and fall apart. As a precaution against the acid working over the top of the box, the upper edge, for an inch or two, should be coated with paraffine over the asphaltum or acid-proof coating.
A cell constructed in this way should accumulate about two volts and one hundred ampere-hours, and will run a one-sixteenth horse-power motor. The expense of making these plates is about twenty-five cents each, and, including the cell and coating materials, each storage-battery will cost approximately two dollars. The lasting qualities of the battery depend on the use or abuse it is put to; but with ordinary care it should last from three to five years.
When the battery ceases to accumulate properly the pile should be removed, and, after washing it thoroughly, the bars should be cut away and new positive plates made and installed. The positive plates are the ones that deteriorate and need replacing; the negatives are almost everlasting, and with proper usage will live for fifteen or twenty years.
Directly the electrolyte is in the cell, connect the poles of your primary cells so as to begin the accumulation of current. Never exhaust the charge of electricity from your storage-cell, and never leave it uncharged when the electrolyte is in, or the plates will be ruined. A battery consisting of from five to twenty bluestone cells will be the best with which to charge this accumulator; and if more than one cell is desired, any number of them can be made and coupled up in series. Take care, when connecting the wires from the primary cells, to see that the positive wire is connected with the positive plates and the negative with the lead bar joining the yellow plates. If by accident you should make a misconnection, bubbles will rise from the electrolyte. This is not right, so reverse the wires and the accumulation of current will then take place without agitation in the cell.
Dry-cells and Batteries
