  BATTERY CHARGING DEVICES The automatic plant most desirable—How an automobile lighting and starting system works—How the same results can be achieved in house lighting, by means of automatic devices—Plants without automatic regulation—Care necessary—The use of heating devices on storage battery current—Portable batteries—An electricity "route"—Automobile power for lighting a few lamps. The water-power electric plants described in preceding chapters are practically automatic in operation. This is very desirable, as such plants require the minimum of care. It is possible to attain this same end with a storage battery plant. Automatic maintenance approaches a high degree of perfection in the electric starting and lighting device on a modern automobile. In this case, a small dynamo geared to the main shaft is running whenever the engine is running. It is always ready to "pump" The same result can be achieved in storage battery plants for house lighting, where the source of power is a gasoline or other engine Take a typical instance where such a plant would be feasible: Farmer Brown has a five horsepower gasoline engine—an ordinary farm engine for which he paid probably $75 or $100. Electric light furnished direct from such an engine would be intolerable because of its constant flickering. This five horsepower engine is installed in the milk room of the dairy, and is belted to a countershaft. This countershaft is belted to the vacuum pump for the milking machine, and to the separator, and to a water pump, any one of which may be thrown into service by means of a tight-and-loose pulley. This countershaft is also belted to a small dynamo, which runs whenever the engine is running. The milking machine, the separator, and the water pump require that the gasoline engine be run on the average three hours each day. The dynamo is connected by wires to the house storage battery through a properly These automatic instruments go still farther in their brainy work. They do not permit the dynamo to charge the battery when the voltage falls below a fixed point, due to the engine slowing down; neither do they permit the dynamo current to flow when the voltage gets too high due to sudden speeding up of the engine. Necessarily, an instrument which will take Such installations are not expensive. A storage battery capable of lighting 8 tungsten lamps, of 16 candlepower each, continuously for 8 hours (or fewer lamps for a longer time); a switchboard containing all the required regulating instruments; and a dynamo of suitable size, can be had for from $250 to $300. All that is necessary to put such a plant in operation, is to belt the dynamo to the gasoline engine so that it will run at proper speed; and to connect the wires from dynamo to switchboard, and thence to the house service. The dynamo required for the above plant delivers 10 amperes at 45 volts pressure, or 10 × 45 = 450 watts. A gasoline, gas, or oil This system is especially desirable where one uses a windmill for power. The speed of the windmill is constantly fluctuating, so much so in fact that it could not be used for electric light without a storage battery. But when equipped with a regulator on the switchboard which permits the current to flow only when the battery needs it, and then only when the speed of the windmill is correct, the problem of turning wind power into electric light is solved. If the farmer does not desire to go to the additional expense of automatic regulation, there are cheaper plants, requiring attention Since the principal item of first cost, as well as depreciation, in a storage battery electric light plant is the storage battery itself, the smallest battery commensurate with needs is selected. Since the amount of current stored by these batteries is relatively small, electric irons and heating devices such as may be used freely on a direct-connected plant without a battery, are rather expensive luxuries. For instance, an electric iron drawing 400 watts an hour while in use, requires as much energy as 20 tungsten lamps of 16 candlepower each burning for the same length of time. Its rate of current consumption would be over 13 amperes, at 30 volts; which would require a larger battery than The use to which electricity from a storage battery is put, however, is wholly a matter of expense involved; and if one is willing to pay for these rather expensive luxuries, there is no reason why he should not have them. Heating, in any form, by electricity, requires a large amount of current proportionally. As a matter of fact, there is less heat to be had in thermal units from a horsepower-hour of electricity than from three ounces of coal. When one is generating current from water-power, or even direct from gasoline or oil, this is not an argument against electric heating devices. But it becomes a very serious consideration when one is installing a storage battery as the source of current, because of the high initial cost, and depreciation of such a battery. Farmers who limit the use of their storage battery plants to lighting will get the best service. Portable Batteries Abroad it is becoming quite common for power companies to deliver storage batteries fully charged, and call for them when discharged. Without a stretch of the imagination, we can imagine an ingenious farmer possessing a water-power electric plant building up a thriving business among his less fortunate neighbors, with an "electricity" route. It could be made quite as paying as a milk route. Connections for charging storage batteries on 110-volt mains Many communities have water or steam power at a distance too great to transmit 110-volt current by wire economically; and because of lack of expert supervision, they do not care to risk using current at a pressure of 500 volts or higher, because of its danger to human life. In such a case it would be quite feasible for families to wire their houses, and carry their Such a battery would necessarily be small, and of the sealed type, similar to those used in automobiles. It could be used merely for reading lamps—or it could be used for general lighting, according to the expense the farmer is willing to incur for batteries. An ordinary storage battery used in automobile ignition and lighting systems is of the 6-volt, 60-ampere type, called in trade a "6-60." Lamps can be had for these batteries ranging in sizes from 2 candlepower to 25 candlepower. A lamp of 15 candlepower, drawing 2½ amperes, is used for automobile To charge such a battery on a 110-volt direct current, it is necessary to install some means of limiting the amount of current, or in other words, the charging rate. This charging rate, for 8 hours should be, as we have seen, one-eighth of the ampere-hour capacity of the battery. Thus a "6-60" battery would require a 7½ ampere current. Connecting two such batteries in "series" (that is, the negative pole of one battery to the positive pole of the second) would make a 12-volt battery. Ten or twelve such batteries The diagram on page 259 shows the connections for charging on a 110-volt circuit. An ordinary 16-candlepower carbon lamp is of 220 ohms resistance, and (by Ohm's Law, C equals E divided by R) permits ½ ampere of current to flow. By connecting 15 such lamps across the mains, in parallel, the required 7½ amperes of current would be flowing from the generator through the lamps, and back again. Connect the battery in "series" at any point on either of the two mains, between the lamps and the generator, being careful to connect the positive end to the positive pole of the battery, and vice versa. Lamps are the cheapest form of resistance; but in case they are not available, any other form of resistance can be used. Iron wire wound in spirals can be used, or any of the many makes of special resistance wire on the market. First it is necessary to determine the amount of resistance required. We have just seen that the charging rate of a 60-ampere hour battery is 7½ amperes. Applying Ohm's Law here, we find that ohms resistance equals volts divided by amperes, or R = 110/7.5 = 14.67 ohms. With a 220-volt current, the ohms resistance required in series with the storage battery of this size would be 29.33 ohms. Automobile Power for Lighting There are many ingenious ways by which an automobile may be utilized to furnish electric light for the home. The simplest is to run wires direct from the storage battery of the self-starting system, to the house or barn, in such a way that the current may be used for reading lamps in the sitting room. By a judicious use of the current in this way, the normal operation of the automobile in the daytime will keep the battery charged for use of the night lamps, and if care is used, such a plan should not affect the life of the battery. Care should be used also, in this regard, not to discharge the battery too low Using an automobile lighting system for house lighting implies that the car be stored in a garage near the house or barn; as this battery is too low in voltage to permit transmitting the current any distance. One hundred feet, with liberal sized transmission wires is probably the limit. That such a system is feasible is amply proved by an occurrence recently reported in the daily papers. A doctor summoned to a remote farm house found that an immediate operation was necessary to save the patient's life. There was no light available, except a small kerosene lamp which was worse than nothing. The surgeon took a headlight off his car, strung a pair of wires through a window, and instantly had at his command a light of the necessary intensity. Another manner in which an automobile engine may be used for house lighting is to let it serve as the charging power of a separate storage battery. The engine can be belted to the generator, in such a case, by means of the fly wheel. Or a form of friction drive can be devised, by means of which the rear wheels (jacked up off the floor) may supply the necessary motive power. In such a case it would be necessary to make allowance for the differential in the rear axle, so that the power developed by the engine would be delivered to the friction drive. 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