If each cell connected in multiple has an electromotive force of 1.5 volts, and can deliver 15 amperes, the total current delivered by this system of connection will be 15 × 5 = 75 amperes with five cells, and the electromotive force will be 1.5 volts as in the case of the single cell. By connecting batteries in multiple, the resistance is reduced, allowing a maximum flow of current. The demand on the individual cells is reduced by multiple connection, as each cell only furnishes a small part of the total current. The greater the number of cells, the less will be the current required per cell, with a given total current. As the life of a battery depends entirely upon the rate at which it is discharged, it is necessary, for economical reasons, to keep the current per cell as small as possible, therefore the multiple system would prove of value as it reduces the load to the smallest possible limit. Enough cells should be placed in multiple to reduce the current to less than a quarter of an ampere per cell. The cells shown will not have sufficient voltage to operate ordinary ignition apparatus requiring a potential of six volts, hence the multiple system must be modified in order to have an increased voltage, and at the same time secure the advantages of multiple connections. (83) Multiple-Series Connections. A compromise is affected by the multiple series system of connections in which are combined the advantages of both the series and multiple systems of connection. This arrangement allows sufficient voltage to operate 6 volt apparatus and at the same time reduces the rate of discharge on the individual cells. The series-multiple battery shown in the diagram 88 consists of four groups of batteries connected in multiple, each group of which consists of five cells that are connected in series. The current and voltage in the various branches is shown in the diagram. The series-multiple system is adapted for use with multiple cylinder engines, as engines with more than one cylinder cause a severe drain on the ignition system. Arranging the series groups in parallel increases the life and efficiency of the cells. If an efficient coil is used, the drain of a single cylinder is not too great to be met with a single set of series cells. If possible the set should be provided with a duplicate, so that the load could be transferred from one set to the other at proper intervals by means of a double throw switch. With a single set of batteries in series the working life of the cells will be approximately twenty hours under ordinary conditions. With four groups of four cells in series, the life of the cell will be approximately 160 hours, or eight times the life of the single set under similar conditions. While the cost of the cells will be only four times that of the single set, it will be seen that the cost of battery upkeep is halved by reducing the demand on the cells.