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Storage-Battery Street-Railway Car.—The first practical power-propelled street-cars were converted horse-drawn types electrified by the use of storage batteries. The defects of the early storage-battery designs and the development of the present overhead feed-wire and trolley, as well as the utilization of high-voltage motors for this purpose, halted development of battery cars for a period. The improvements that have been made in modern storage batteries show that it can now occupy a position of importance in the transportation field. A variety of systems of street-car propulsion are available, each having a distinct field of usefulness. They may be divided into broad classes, one whose units are supplied with power from a central station, with which they must always be in contact, and those employing selfcontained units. In the first class, we have third-rail, cable-conduit and trolley systems; in the second are grouped storage-battery and gasoline-electric types. The Electric Storage Battery Company have made a study of the battery car problem, and with the co-operation of the car builder and electrical apparatus manufacturer, types have been designed that are especially adapted for street-car work. Cars of very high speed and power have been successfully propelled by storage-battery current, as well as the single-truck cars used in belt-line service.
Among the situations which may present conditions favorable to the use of storage-battery cars are the following:
1. Short rural lines not connected with other systems, yet meeting a distinct transportation need.
2. Extensions or spurs to existing electric systems, serving districts which it is desirable to develop, but where the immediate traffic will not justify overhead construction investment.
3. Lines operated to meet some local and special transportation demand other than general public service, as, for example, between mills or factories and a main railroad depot or residential center, plantation railroads, belt-line service in large manufacturing plants, and the like.
4. For the operation of branch lines or extensions used only during certain seasons of the year, as in connection with seaside and summer resorts, amusement parks and the like.
5. As an adjunct to steam lines to supplement the regular steam-train service, furnish local service at short intervals and to branch lines; particularly on roads devoted largely to freight traffic, where there is need of a passenger service, but insufficient traffic to justify regular steam-train operation.
6. Where local ordinances or other reasons do not permit the use of overhead trolley construction.
7. For providing infrequent night or "owl” service.
The storage battery for a single-truck car is located beneath longitudinal car seats in ventilated compartments, and can be easily reached for inspection by removing the seats and thus exposing the battery cell tops. It is composed of 58 cells, of type MV29 Exide, having a capacity of 67 amperes for six hours' continuous discharge at an average of 114 volts. The cells are contained in substantial wooden trays, each containing four cells. Fourteen such trays are provided, the total number of cells
mounted in this manner being fifty-six. Two extra cells are needed to bring the battery up to the desired capacity, these being carried in smaller individual trays. The trays are convenient units for easily removing the battery from the car if necessary, but as it may be charged in place and electrolyte readings and evaporation loss compensated for by removing the seats, in ordi
Fig. 77.–Storage-Battery-Propelled Street-Railway Cars. At Top
Single-Truck Car for Belt-Line Work in Cities. Below it, Fast
nary operation the battery need not be removed from the car. The total weight of the battery is 4,876 pounds. The cells are practically of the same general construction as heavy motor-truck batteries, being of the sealed type. Cars equipped with a battery of this capacity will take a 7 per cent. grade with full passenger load and attain speeds of 15 miles per hour on level track. Under average operating conditions, the input to the car motors, which are of the automobile type, will average 450 watt-hours per car mile. At this rate a car will make 100 miles on a single battery charge on the basis of the six-hour battery capacity specified. In actual service the cars have been run 120 miles per charge. The total weight of such a car is 14,000 pounds, including battery. The seating capacity is sufficient for 26 persons, and the car is 18 feet long
Larger cars, 28 feet long, of the two-truck type, have a seating capacity for 36 persons. The battery for such cars is 88 cells, of type MV 29 Exide battery having a capacity of 67 amperes for six hours' continuous discharge at an average of 173 volts. The battery is contained in 44 trays of 2 cells each. The battery weight is 7,392 pounds, and total weight of car, including battery, is 13 tons. The maximum speed possible is 25 miles per hour, and the current consumption is about 700 watt-hours per car mile. The range of action is 80 miles on one charge. As is true of the smaller car, the battery is carried under the longitudinal seats. In some larger cars, such as shown at the bottom of Fig. 77, the batteries are mounted under the car floor similar to a train-lighting battery, and occupy all the available space between the trucks. When this method of installation is followed the cells are mounted in easily handled trays, as in lighting service.
Submarine Boat Batteries.-One of the most spectacular applications of the storage battery is to submarine boat propulsion when these are under water. On the surface, the craft is propelled by Diesel type internal-combustion engines, which deliver part of their power to generators, which keep the batteries charged. Of course, when submerged, the internal-combustion engines must be shut off and the stored energy of the battery drawn on to drive the boat; the generator becomes a motor for ship propulsion and derives power from the battery it had previously charged. In addition to the main driving motors, there are several others for pump actuation, steering, etc., all of which use battery current. A sectional view of a typical submarine using the Edison alkaline Drop Keel. 5—Habitable Superstructure. 6—Escape and Safety es. 12_Torpedo Firing Tank. 13—Anchor. 14—Periscopes. torage Battery. 22—Galley. 23—Steering Gear. 24Binnacle. and Engines. 31–After Engine-Room and Engines. 32–Cenery Room. 38–Hydroplane. 39—Vertical Rudders. 40—Signal