For ordinary household work as that of operating doorbells, etc., the cells which form a battery are joined in series, that is the positive or carbon pole of one cell is joined to the zinc or negative pole of the next. The cells so connected are placed in circuit with the bell and push button. If by accident the two cells of a battery are joined with both carbon poles or both zinc poles together the battery will give out no current because the voltage is opposed.

In the use of batteries for ignition as for gasoline engines, automobiles, etc., the arrangement of the cells has frequently a decided influence on the effect produced. In Fig. 256 A is represented four cells joined in series, that is the carbon or + poles are joined with the zinc or - poles, alternately. Connected in this manner if each cell gives 1.5 volts the battery will give 4 X 1.5 = 6 volts; the current, however, will remain as that of a single cell. If the cells singly give 20 volts, the battery will give 20 volts. When cells are connected in this form the current passes through each cell in turn and is as much a part of the circuit as the wires. Should one of the cells be "dead" - that is delivering no current - it will act as additional resistance and the current is reduced.

When joined in multiple or parallel connection as in Fig. 256 B, in which all similar binding posts are connected, the effect is decidedly different. In the multiple connection all of the zincs are joined to act as a single zinc and all of the carbons are likewise joined and act as a single carbon. In such a combination the voltage will be that of a single cell 1.5 volts, but the amperage will be four times that of a single cell or 80 amperes.

The diagrams and following descriptions of possible combinations were taken from a bulletin on battery connections issued by the French Battery and Carbon Co.

By combining the series and multiple connections, as shown in Fig. C, both the voltage and current can be increased over that delivered by one cell. Referring to the figure, it is seen that in each of the two rows of four cells the cells are connected in series. This would produce 6 volts and 20 amperes for the series of four which may now be assumed as a unit, so that the two rows can be imagined as two large cells, each of which has a normal output of 20 amperes at 6 volts. Now by connecting the similar poles of two such large cells they are in multiple and we get an increased current or 40 amperes and 6 volts, which is the capacity of the eight cells connected as shown in the figure. This is commonly designated as a multiple-series battery.

Fig. 256 D illustrates a multiple-series connection made in a different manner, but which produces the same voltage and current as the above mentioned. In Fig. D, two cells at a time are connected in multiple, and these sets are then connected in series. The capacity of each set of two is 40 amperes at 1 1/2 volts, and as these four sets are connected in series the total output of the eight cells combined is 6 volts and 40 amperes, the same as that produced by the connections shown in Fig. C.

Fig. E shows the multiple-series connection illustrated in Fig. D, applied to twelve cells in which four sets of three cells each are wired in series, the three cells of a set being in multiple so that the capacity of a set is 1 1/2 volts and 60 amperes. By connecting the four sets in series as shown, the total capacity will be 60 amperes at 6 volts.

The use of the series - multiple connection is a distinct step forward in dry-cell use. The arrangement of cells shown in Figs. C or D is better than the arrangement in Fig. A, in just the same way that a team of horses is better than a single horse. One horse pulling a load of 2 tons may become exhausted in one hour, but two horses pulling that same load may work continuously for six hours. It is true that in Fig. C there are twice as many cells used as in Fig. A, but the eight cells in Fig. C will do from three to four times as much work as the four cells in Fig. A. In other words, while more cells are used in the multiple-series arrangement, the amount of service per cell is greater and the service is, therefore, cheaper in the multiple-series arrangement.

Some battery manufacturers sell their batteries put up in boxes, the cells being connected up in multiple-series and surrounded by pitch or tar to keep out the moisture. This has certain advantages as well as certain disadvantages. One of the objections to this method of putting up dry cells is that if by any chance one cell out of the eight or twelve which are buried in the pitch is defective it will run all of the cells down, and being buried offers no means of detection or removal. It is not possible to guarantee absolutely that a weak cell will not be occasionally included in a large number, so dry cells may be expected to vary to some degree among themselves.

It is interesting to know the effect of one weak cell on a series-multiple arrangement. If, for example, in Fig. C or Fig. D, the dotted line connecting (a) and (b) be used to indicate a cell which is partly short-circuited by internal weakness or external defect the result is as follows:

In the arrangement shown in Fig. C, where one cell of the upper four is short-circuited, the lower four will discharge through the upper four even though the external circuit is not closed; that is, one short-circuited cell will cause a run-down in all of the cells. In Fig. D, however, one short-circuited cell will influence not the entire set but the other one to which it is directly connected. There is thus seen to be an advantage in the arrangement of Fig. D and Fig. E, over the arrangement in Fig. C.

In making connections between cells insulated wire should be used, or special battery connectors are preferably employed. The ends of the wires or connectors and the binding posts must be scraped clean so that good electrical connection can be made between the two, and the knurled nuts should be screwed tight into place. Care must also be taken that the pasteboard covering around the battery is not torn. This would allow contact between the zinc containers, and thus short-circuit the cells. The batteries should be placed so that the zinc cans and the binding posts of any cell do not come into contact with any other cell. Vibration might cause enough motion for the brass terminal to wear through the pasteboard of the neighboring cell and make contact with the zinc can.

Different classes of work require different amounts of current at different voltages and by choosing the proper combination of series, multiple, or series-multiple connections practically every requirement can be fulfilled. For electric bells, telegraph instruments, miniature lights, toy motors with fine wire windings, etc., series connection is recommended for the reason that the resistance of the external circuit is high and a large voltage is necessary. For spark coils, magnets and toy motors with large wire windings, multiple or series-multiple connection of batteries should be used as a high voltage is not required.

For some work, gas-engine ignition especially, it is economical to have two complete sets of batteries, either of which can be thrown into the circuit at will, so that while one set is delivering current the other is recuperating. It has been estimated that by using two sets of batteries, properly connected to give the desired current, the life of each set is increased about four times. Thus it is seen that a saving of 50 per cent. is effected in the cost of the batteries.