Fig. 47. SECONDARY BATTERY.

Battery, Secondary.

A voltaic battery whose positive and negative electrodes are formed or deposited by a current from a separate source of electricity by electrolysis. On disconnection the battery is ready to yield a current, in the reverse direction of that of the charging current. The usual type has lead plates on one of which lead binoxide and on the other of which spongy lead is formed. The lead binoxide seems to be the negative element, and it also acts as the depolarizer. The spongy lead is the positive electrode. The solution is dilute sulphuric acid of specific gravity 1.17. The action consists first in the oxidation of the spongy lead. The hydrogen set free by the reaction, and which by electrolytic transfer goes to the other plate, reduces the lead binoxide to protoxide. The sulphuric acid then attacks the oxides and converts the oxides into sulphates.

The charging process consists in sending a current in the reverse direction through the battery. If there are several cells they are arranged in series, so that each one receives the same intensity of current. An electrolytic decomposition takes place, the lead sulphate on one plate is reduced to metallic lead, and that on the other plate is oxidized to lead binoxide. It is then ready for use.

71 STANDARD ELECTRICAL DICTIONARY.

The plates in a lead plate battery are of very large area per cell, and are placed close together. Sometimes, as in Plant?'s battery, large flat plates are laid together with a separating insulator between them, and are then rolled into a spiral. Sometimes, the most usual arrangement, the plates are in sets, the positive and negative ones alternating, and each cell containing a number of plates.

To secure a good quant.i.ty of active material, the plates are sometimes perforated, and the perforations are filled with oxide of lead. This gives a good depth of material for the charging current to act on, and avoids the necessity for a tedious "forming," q. v.

The electro-motive force of such a battery per cell is 2 volts. Its resistance may only be one or two-hundredths of an ohm. An intense current of many amperes can be supplied by it, but to avoid injuring the cell a current far less than the maximum is taken from it.

To charge it, a slightly greater electro-motive force, the excess being termed spurious voltage, is required.

Fig. 48. SIEMENS' AND HALSKE'S PAPER PULP BATTERY.

72 STANDARD ELECTRICAL DICTIONARY.

Battery, Secondary, Plante's.

Plante's secondary battery is one of the earlier forms of storage battery, but has had much success. Two lead plates, large in area and close together but not touching, are "formed," by exposure to an electrolyzing current of electricity in one direction, while they are immersed in dilute sulphuric acid. This converts the surface of one plate into binoxide. The cell is then allowed to discharge itself almost completely, when the charging current is again turned on. This process is repeated over and over again, until the surfaces of the plates are considerably attacked, one plate, however, being maintained in a state of oxidation. After a few days of this operation a period of rest is allowed between the reversals, which sets up a local action on the oxidized plate, between the metallic lead of the plate, and its coating of binoxide. This causes the lead to be attacked, under the influence of the local couple, and sulphate of lead is formed, which, ultimately, by the charging current is converted into peroxide. These operations produce an exceedingly good battery. The process described is termed forming.

The plates separated by strips of insulating material are generally wound into a double spiral.

Battery, Siemens' and Halske's.

A Daniell battery of peculiar shape. The copper, C, is at the bottom of the gla.s.s jar, A. The inner jar, K, has the form of a bell, and supports a ma.s.s of paper pulp, which is dampened with sulphuric acid. The zinc, Z, rests on top of the ma.s.s of pulp. The battery is very durable, but of high resistance.

Battery, Sir William Thomson's.

A form of Daniell battery, of the gravity type. The receptacles are shallow wooden trays lined with lead. A thin plate of copper rests on the bottom. The zinc plate is of gridiron shape, and rests on wooden blocks which support it in a horizontal position above the copper. One tray is placed on top of the other, the upper tray resting on the corners of the zinc plate which rise above the level of the top of the flat vessel. Thus connection is a.s.sured without wires or binding posts.

It is charged like a gravity battery. The density of the zinc sulphate solution should be between 1.10 and 1.30. The circuit must be kept closed to prevent deposition of metallic copper on the zinc. The entire disposition of the battery is designed to reduce resistance.

Battery, Skrivanow.

A pocket battery of the De la Rue type, with a solution of 75 parts caustic potash in 100 parts of water as the excitant. The silver chloride is contained in a parchment paper receptacle. Its electro-motive force is 1.45 to 1.5 volts.

Battery, Smee's.

A single fluid combination, with zinc positive plate, and a plate of silver, coated with platinum black, for the negative plate. The finely divided platinum affords a surface from which the hydrogen bubbles instantly detach themselves, thus preventing polarization. The liquid is a mixture of one part sulphuric acid to seven parts of water. For the negative plate silver-plated copper, coated with platinum black, is used. Electromotive force, .47 volt.

Fig. 49. SMEE'S BATTERY.

73 STANDARD ELECTRICAL DICTIONARY.

Fig. 50. SPIRAL BATTERY, OR HARE'S DEFLAGRATOR.

Battery, Spiral.

A battery whose plates of thin zinc and copper are wound into a spiral so as to be very close, but not touching. Dilute sulphuric acid is the excitant. It is now practically obsolete.

Synonyms--Calorimeter--Hare's Deflagrator.

Battery, Split.

A battery of a number of voltaic cells, connected in series, with their central portion grounded or connected to earth. This gives the ends of opposite potentials from the earth, and of difference therefrom equal to the product of one-half of the number of cells employed, multiplied by their individual voltage.

Battery Solutions, Chromic Acid.

A number of formulae have been proposed for these solutions. (See Electropoion Fluid--Kookogey's Solution--Poggendorff's Solution-- Trouv?'s Solution--Delaurier's Solution--Chutaux's Solution--Dronier's Salt--Tissandier's Solution.)

Battery, Trough.

A battery whose elements are contained in a trough, which is divided by cross-part.i.tions so as to represent cups. A favorite wood for the trough is teak, which is divided by gla.s.s or slate part.i.tions. Marine glue or other form of cement is used to make the joints tight. For porous cup divisions plates of porous porcelain or pottery are placed across, alternating with the impervious slate part.i.tions.

Battery, Trouv?'s Blotting Paper.

A battery of the Daniell type in which the solutions are retained by blotting paper. A considerable thickness of blotting paper lies between the two plates. The upper half of the thickness of the blotting paper is saturated with a solution of zinc sulphate, on which the zinc plate rests.

The lower half of the paper is saturated with copper sulphate solution, and this rests upon the copper plate.

Fig. 51. TROUV?'S BLOTTING PAPER BATTERY.

74 STANDARD ELECTRICAL DICTIONARY.

Battery, Tyer's.

A modification, as regards the positive element, of Smee's battery, q.

v. The bottom of the battery jar contains a quant.i.ty of mercury in which pieces of zinc are thrown, and this const.i.tutes the positive element.

A ball of zinc at the end of an insulated copper wire affords the connection with the zinc and mercury. Its great advantage is that the smallest sc.r.a.ps of zinc can be used in it, by being dropped into the mercury. The negative plate is platinized silver; the exciting liquid, dilute sulphuric acid.

Fig. 52. TYER'S BATTERY.