Chapter II

CELLS AND BATTERIES

Simple Cells

In order to generate electricity it is necessary to employ cells, batteries, or dynamos. Since the construction and operation of a dynamo is somewhat intricate, it will be better to start with the simpler methods of electric generation, and so work up to the more complicated forms. For small apparatus, such as electric bells and light magnets and motors, the zinc-carbon-sal-ammoniac cell will answer very well; but for larger machinery, where more current is required, the bluestone and the bi-chromate batteries will be found necessary.

A simple and inexpensive cell may be made from electric-light carbons, with the copper coating removed, and pencils of zinc, such as are used for electric-bell batteries and which can be purchased for five cents each. Copper wire is to be bound around the top of each pencil of carbon and zinc, and firmly fastened with the pliers, so that it will not pull off or become detached. It will be well to cut a groove with a file around the top of both the carbon and zinc, into which the wire will fit. The elements should then be clamped between two pieces of wood and held with screws, as shown in Fig. 1. A more efficient carbon pole is made by strapping six or more short carbon pencils around one long one, as shown in Fig. 3. The short pieces of electric-light carbons are bound to the longest carbon with heavy elastic bands, or cotton string dipped in paraffine or wax, to make the cotton impervious to water and the sal-ammoniac solution.

Another arrangement of elements is shown in Fig. 2, where a zinc rod is suspended between two carbons, the carbons being connected by a wire that must not touch the zinc.

A fruit-jar, or a wide-necked pickle-bottle, may be employed for a cell, but before the solution is poured in, the upper edge of the glass should be coated with paraffine. This should be melted and applied with a brush, or the edge of the glass dipped in the paraffine.

The solution is made by dissolving four ounces of sal-ammoniac in a pint of water, and the jar should be filled three-fourths full. In this solution the carbons and zinc may be suspended, as shown in the illustration (Fig. 4) of the sal-ammoniac cell. The wood clamps keep the carbon and zinc together, and the extending ends rest on the top of the jar and hold the poles in suspension. Plates of zinc and carbon may be clamped on either side of a square stick and suspended in the sal-ammoniac solution, as shown in Fig. 5, taking care, however, that the screws used for clamping do not touch each other.

If one cell is not sufficiently powerful, several of them may be made and coupled up in series--that is, by carrying the wire from the zinc of one to the carbon of the next cell, and so on to the end, taking care that the wire from the carbon in the first cell and that from the zinc of the last cell will be the ones in hand, as shown in Fig. 6. This constitutes a battery. Be sure and keep the ends of the wire apart, to prevent galvanic action and to save the power of the batteries.

This battery is an excellent one for bells and small experimental work, and when inactive the zincs are not eaten away (as they would be if suspended in a bi-chromate solution), for corrosion takes place only as the electricity is required, or when the circuit is closed. A series of batteries of this description will last about twelve months, if used for a bell, and at the end of that time will only require a new zinc and fresh solution.

The cell in which the plates shown in Fig. 5 are used may contain a bi-chromate solution; and for experimental work, where electricity is required for a short time only, this will produce a stronger current. But remember that the solution eats the zinc rapidly, and the plates must be removed as soon as you have finished using them.

The bi-chromate solution is made by slowly pouring four ounces of commercial sulphuric acid into a quart of cold water. This should be done in an earthen jar, since the heat generated by adding acid to water is enough to crack a glass bottle. Never pour the water into the acid. When the solution is about cold, add four ounces of bi-chromate of potash, and shake or mix it occasionally until dissolved; then place it in a bottle and label it:

BI-CHROMATE BATTERY FLUID

POISON

Before the zincs are immersed in the bi-chromate solution they should be well amalgamated to prevent the acid from eating them too rapidly.

The amalgamating is done by immersing the zincs in a diluted solution of sulphuric acid for a few seconds, and then rubbing mercury (quicksilver) on the surfaces. The mercury will adhere to the chemically cleaned surfaces of any metal except iron and steel, and so prevent the corroding action of the acid. Do not get on too much mercury, but only enough to give the zinc a thin coat, so that it will present a silvery or shiny surface.

A two-fluid cell is made with an outer glass or porcelain jar and an inner porous cup through which the current can pass when the cup is wet. Fig. 7.

A porous cup is an unglazed earthen receptacle, similar to a flower-pot, through which moisture will pass slowly. The porous cup contains an amalgamated plate of zinc immersed in a solution of diluted sulphuric acid--one ounce to one pint of water. The outer cell contains a saturated solution of sulphate of copper in which a cylindrical piece of thin sheet-copper is held by a thin copper strap, bent over the edge of the outer cell. A few lumps or crystals of the copper sulphate, or bluestone, should be dropped to the bottom of the jar to keep the copper solution saturated at all times. When not in use, the zinc should be removed from the inner cell and washed off; and if the battery is not to be employed for several days, it would be well to pour the solutions back into bottles and wash the several parts of the battery, so that it may be fresh and strong when next required. When in action, the solutions in both cups should be at the same level, and be careful never to allow the solutions to get mixed or the copper solution to touch the zinc. Coat the top of the porous cell with paraffine to prevent crystallization, and also to keep it clean. Take great care, in handling the acid solutions, to wear old clothes, and do not let the liquids spatter, for they are strong enough to eat holes in almost anything, and even to char wood. The two-fluid cells are much stronger than the one-solution cells, and connected up in series they will develop considerable power.

For telegraph-sounders, large electric bells, and as accumulators for charging storage-batteries, the gravity-cell will give the most satisfactory results. The one shown in Fig. 8 consists of a deep glass jar, three strips of thin copper riveted together, and a zinc crow-foot that is caught on the upper edge of the glass jar. These parts will have to be purchased at a supply-house, together with a pound or two of sulphate of copper (bluestone).

To set up the cell, place the copper at the bottom and drop in enough of the crystals to generously cover the bottom, but do not try to imbed the metallic copper in the crystals; then fill the jar half full of clear water. In another jar dissolve two ounces of sulphate of zinc in enough water to complete the filling of the jar to within two inches of the top; then hang the zinc crow-foot on the edge of the jar so that it is immersed in the liquid and is suspended about three inches above the top of the copper strip. The wire that leads up from the copper should be insulated with a water-proof coating and well covered with paraffine. A number of these cells may be connected in series to increase the power of the current, and for a working-battery this will show a high efficiency. Note that at first the solutions will mingle. To separate them, join the two wires and start the action; then, in a few hours, a dividing line will be seen between the white, or clear, and the blue solutions, and the action of the cell will be stronger. After long-continued use it may be necessary to draw off some of the clear zinc sulphate, or top solution, and replace it with pure water. The action of the acids reduces the metallic zinc to zinc sulphate and deposits metallic copper on the thin copper strips, and in this process an electrical current is generated.

A Plunge-battery

When two or more cells (in which sulphuric acid, bi-chromate of potash, or other strong electropoions are employed) are coupled in series, it would be well to arrange the copper and zinc, or the zinc and carbon, poles on a board, so that all of them may be lowered together into the solutions contained in the several jars. A simple arrangement of this kind is shown in Fig. 9, where a rack is built for the jars and at the top of the end boards a projecting piece of wood, supported by a bracket, is made fast. A narrow piece of board nearly the length of the jar-rack is fitted with the battery-poles, as shown at Fig. 9 A. The carbon and zinc, or copper and zinc, poles are attached to small blocks of wood (as described for Fig. 5), and this block in turn is fastened to the under side of the board with brass screws. The poles of the cells are to be connected (as explained in Fig. 6), and when the battery is in use the poles are immersed in the solution contained in the jars. When the battery is at rest the narrow board should be lifted up and placed on the projecting arms of the rack, so that the liquid on the poles may drain into the jars directly underneath. One or more of these battery-racks may be constructed, but they cannot be made to hold conveniently more than four or six cells each; if more cells are required, those contained in each rack must be coupled up in series.

A simpler plunge-battery is shown in Fig. 10. A cell-rack is made of wood and given two or three coats of shellac. The narrow board (to the under side of which the battery-poles are attached, as explained in Fig. 9) is hung on chains or flexible wires, which in turn are made fast to an iron shaft running the entire length of the cell-rack. This shaft is of half-inch round iron, and is held in place, at one end, by a pin and washer; while at the other the end is filed with a square shoulder, and a handle and crank is fitted to it, so that the shaft may be turned. A small hole, made at the side of the crank when it is hanging down, will receive a hard-wood peg, or a steel nail, and this will prevent the crank from slipping when the board holding the poles is raised. If a gear-wheel and tongue can be had to fit on the shaft, it will then be possible to check the shaft securely at any part of a turn of the crank. The battery-poles are to be connected in series along the top of the portable board, as explained for Fig. 6. When two or more of these plunge-batteries are used at one time, the wire from the carbon of one is to be connected with the zinc pole of the next, and so on. The wire from the zinc of the first battery, and the wire from the carbon of the last battery, will be the ones available for use.

A Storage-battery

When more current is desired than the simple batteries will give, a storage-battery should be employed as an accumulator. This result can be secured by coupling primary cells in series, so that they will be constantly generating and feeding the battery. Storage-batteries are too heavy to be shifted about, like single cells or small plunge-batteries; they should be placed in a cellar, where the charging or primary cells can be located close by, and, unless positively necessary, the battery of cells and the accumulator should not be moved.

With sufficiently large insulated wires (Nos. 12, 14, or 16 copper), the current may be carried to any part of the house for use in various ways--such as running a light motor or a fan, lighting a lamp-circuit, or fusing metals and chemicals for experimental purposes. While the battery to be described is not a light one in weight, nor as economical as the improved new Edison storage-battery, it is a good and constant one, and, if not overcharged or abused, will last for several years.

The component parts of a storage-battery are lead in metallic and chemical form, the electrolyte, or fluid, in which the plates are immersed, and the water-tight and chemical-proof cell or container. From a plumber, a supply-house, or a lead-works, obtain a quantity of three-eighth by one-quarter-inch strip-lead of the kind called chemical, or desilverized; also a larger quantity of lead-tape, one-sixty-fourth of an inch thick and three-eighths of an inch wide. This last is also known as torpedo-lead, and is kept by electrical supply-houses.

If the three-eighths by quarter-inch strip-lead cannot be had, then purchase eight or ten pounds of heavy sheet-lead, and, with a tin-shears, divide it into strips three-eighths of an inch wide and twenty-nine inches long, taking care to cut it of uniform width and with true edges. From hard-wood three-eighths or half an inch thick, cut a block six by seven inches and make four countersunk holes in it, so that it may be screwed fast to a table or bench, as shown in Fig. 11 A. Around this the lead strips should be shaped and beaten at the corners to make the angles sharp.

From the three-eighths by quarter-inch, or sheet-lead strips, make seven frames as shown in Fig. 12. This is done by binding a strip of the lead around the block, as shown at Fig. 11 B. Where the ends come together insert a short piece of lead, three-eighths or half-inch, as shown at Fig. 12 A, and solder it fast. A soldering-iron may be heated with a Bunsen-burner gas-flame or in a charcoal fire. However, if gas is available, it would be better to use the blue flame from a Bunsen burner and direct the hot blast directly on the work with a blow-pipe, and so fuse the lead points together. After a little practice with the blow-pipe it will be used for many pieces of work in preference to the soldering-iron. If the sheet-lead is used for the frames in place of the three-eighths by quarter-inch strips, two or three strips will have to be taken, so as to build up the band of the frame to about a quarter of an inch in thickness. When soldered together, or fused at the edges, these built-up frames will be as rigid as the solid metal.

Now cut a number of strips of the thin lead-tape six inches and a half long, and others that will necessarily be somewhat longer, for each frame is to be filled with straight and crimped pieces, as shown in Fig. 13. If there is a fluting-iron in the house, the crimping may be done in the brass gears at one end of the machine. Or two wheels may be cut from hard-wood with a fret-saw, and made fast to a block with screws, as shown in Fig. 14. A handle, attached to one wheel, will make it possible to turn the gears; and they should be placed just far enough apart to allow the tape to pass through without tearing or squeezing. Put a washer between the wheel and the block to prevent friction.

When a frame is in the position shown in Fig. 13, and lying on a piece of slate or flat stone, you will first put in a crimped piece of tape, as shown at Fig. 13 A, and under this arrange a straight piece (Fig. 13 B); then, with the blow-pipe and flame, fuse fast to the frame and catch the flutes of the crimped piece to the straight one every inch or two. Add alternate crimped and straight strips until the frame is filled and presents the appearance of Fig. 13. When the seven frames are ready, lay three of them aside for the positives and four for the negatives. Note that the positives are red and the negatives a dark yellow when they are filled with the active material.

There are several methods of depositing the active material in the mesh or net-work of the plates, but some of them are too technical, others too complicated, and still others require charging machinery. The following plan will be the simplest and easiest for the amateur:

At a paint-store, or from a wholesale druggist, obtain several pounds of oxide of lead (red-lead) and a similar quantity of litharge (yellow-lead). In an earthen vessel, or large jar, make a solution composed of water, twenty ounces, and commercial sulphuric acid, two ounces. This is the mixture commonly known as “one to ten.” Place some red-lead (dry) in an old saucepan or soup-plate, and add a little of the acid solution: then, with an old table-knife or small trowel, mix the lead into a stiff paste, like soft putty. Do not get it too thin or it will run; nor too thick, as then it will not properly adhere to the lead-mesh of the frames. With the frame lying on its side, plaster in the red composition between the flutes and fill up the frame solid with it. Treat all three of the positive frames in the same manner, taking care that the exposed surfaces of the composition-filling is smooth and flush with the edges of the lead frame and mesh. Do not disturb these plates for a while, but let them remain in position, so as to set and partially dry. Add acid solution to the yellow-lead in a similar manner, and fill the four negative plates. When partially dry, the plates will be ready to combine in a pile.

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

Dry-cells are extensively used nowadays, since their cleanliness, high efficiency, and low internal resistance make them preferable to the Leclanché and other open-circuit batteries for bells, annunciators, and other light work. In the dry-cell, the electrolyte, instead of being a liquid, is a gelatinous or semi-solid mass, which will not run nor slop over. When the capping of pitch or tar is in place, the cell may be placed in any position, with full assurance that the electrolyte will not become displaced nor run out. Dry-cells may be made of almost any size for convenience of handling, but those commonly used vary from one to four inches in diameter, and from four to fifteen inches high. For bells and general electric work, a cell two inches and a half in diameter and seven inches high will be found a convenient size to make and handle.

The component parts of a dry-cell are the cell itself (which is made of zinc and acts as the positive pole), the carbon, the electrolyte or active excitant element, and the pitch or tar cap to hold the electrolyte and carbon in place.

From a tinsmith obtain some pieces of sheet zinc, and roll them into cylindrical form as shown in Fig. 18 A. The sheets should measure seven by eight inches, and when formed the edges are to be lapped and soldered.

From a smaller piece of zinc cut round bottoms, fit them in the cylinders and solder securely in place, taking care to close up all seams or joints to prevent the escape of the electrolyte.

From a supply-house obtain battery-carbons, one inch and a half wide by half or three-eighths of an inch thick and eight inches long. These should be provided with a thumb-screw or small bolt and nut at the top so as to make wire connections with the carbon. A strip of zinc should be soldered to the outside upper edge of the zinc cup to which wire attachments may be made with thumb-screws or small bolts and nuts. When the parts are ready to assemble, make a wooden mould or form a trifle larger than the carbon. This is intended to act as a temporary plunger, and is inserted, at first, in place of the carbon plate. This wooden plunger should be smooth, and given a coat of shellac to prevent it from absorbing any moisture.

Insert the plunger in the zinc cup and support it so that it will be at least half an inch above the bottom and centred at the middle of the cup. The electrolyte is then placed in the cup, and, when it has set a little, the wooden plunger is removed and the carbon inserted in its place.

The electrolyte is composed as follows:

Ammonium chloride 1 part Zinc chloride 1 part Plaster of Paris 3 parts Flour ¾ part Water 2 parts

Mix these together and place the compound within the zinc cups, so that the mass settles down and packs closely about the plunger. The space left unfilled about the carbon should be filled with a mixture composed as follows:

Ammonium chloride 1 part Zinc chloride 1 part Manganese binoxide 1 part Granulated carbon 1 part Flour 1 part Plaster of Paris 3 parts Water 2 parts

These proportions may be measured in a tin cup, a table-spoon, or any other small receptacle. Note that the measurement by parts is always by bulk and not by weight.

Do not fill the zinc cup to the top, but leave an inch of space, so that half an inch of sealing material may be added. See that the inside top edge of the zinc cup is clean; then melt some tar or pitch and pour it over the top of the electrolyte, so that it binds the zinc cup and carbon into a solid form. Drive an awl down through the capping material when it is nearly dry, and leave the holes open for the escapement of gases.

Give the outer surface of the zinc cells a coat of asphaltum varnish, and wrap several thicknesses of heavy paper about them to prevent contact and short-circuiting. Protect the bottoms in a similar manner, and as a result you will have a cell that will appear as shown in Fig. 18 B. A battery of cells powerful enough for any light work can be made by connecting the cells in series, each having an electro-motive force of one and a half volts, with an internal resistance of less than one-third of an ohm.