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Page 25
M. Trouve exhibited a small boat and a tricycle, both worked by Plante
accumulators, at Paris, in 1881.
The first locomotive actuated by storage batteries was used at a
bleaching works in France in 1882. During the same year I designed an
electric street car for the storage company, and this was tried on the
lines of the West Metropolitan Tramways in March, 1883. It had
accommodation for 46 passengers. This car had many defects, and I
reconstructed it entirely, and ran it afterward in its improved form
on the South London Tramways, and also on a private track at Millwall,
where it is now in good condition, and I have a similar car in Berlin.
M. Phillippart exhibited a car in Paris and M. Julien made successful
experiments in Brussels, Antwerp, and Hamburg. Mr. Elieson is running
storage battery locomotives in London. Mr. Julien has also been
experimenting with a car in New York, and I believe one is in course
of construction for a line in the city of Boston. Messrs. W. Wharton,
Jr. & Co. have a storage battery car running at Philadelphia on Spruce
and Pine streets, and this energetic firm is now fitting up another
car with two trucks, each carrying an independent motor, similar to my
European cars.
I have mentioned all these facts in order to show that there is a
considerable amount of activity displayed in the matter of storage
batteries for street cars, and that continued and substantial progress
is being made in each successive case. The prejudices against the
application of secondary batteries are being rapidly dispelled, and
there are indications everywhere that this method of propulsion will
soon take a recognized place among the great transit facilities in the
United States. I feel convinced that this country will also in this
respect be far ahead of Europe before another year has passed over our
heads.
There are several popular and I may say serious objections to the
employment of storage batteries for propelling street cars. These
objections I will now enumerate, and endeavor to show how far they are
true, and in what measure they interfere with the economical side of
the question.
First objection: The loss of energy, which amounts in practice to 20
and sometimes 30 per cent. Now, every method of storing or
transmitting energy involves some waste, but in saying this we need
not condemn the system, for after all the term efficiency is only a
relative one. For instance, a 10 horse power steam engine consumes
three times as much fuel per horse power hour as a 1,000 horse power
engine does, yet this small engine must be, and is regarded as, one of
the most economical labor-saving appliances known to us. Considered as
a heat engine, the efficiency of the most economical steam motor is
but ten per cent.--90 per cent of the available units of heat
contained in coal being lost during its transformation into mechanical
energy. Thus, if we find that the storage battery does not return more
than 70 per cent, of the work expended in charging it, we ought not to
condemn it on that account until we have ascertained whether this low
efficiency renders the system unfit for any or all commercial
purposes. It is needless to go into figures in order to show that,
when compared with animal power, this objection drops into
insignificance.
The second, more formidable, objection relates to the weight of
storage batteries--and this involves two disadvantages, viz., waste of
power in propelling the accumulator along with the car, and increased
pressure upon the street rails, which are only fitted to carry a
maximum of 5 tons distributed over 4 points, so that each wheel of an
ordinary car produces a pressure of 1� tons upon a point of the rail
immediately under it.
The last mentioned objection is easily overcome by distributing the
weight of the car with its electrical apparatus over 8 wheels or 2
small trucks, whereby the pressure per unit of section on the rails is
reduced to a minimum. With regard to the weight of the storage
batteries, relatively to the amount of energy the same are capable of
holding and transmitting, I beg to offer a few practical figures.
Theoretically, the energy manifested in the separation of one pound of
lead from its oxide is equivalent to 360,000 foot pounds, but these
chemical equivalents, though interesting in themselves, gives us no
tangible idea of the actual capacity of a battery.
Repeated experiments have shown me that the capacity of a secondary
battery cell varies with the rate at which it is charged and
discharged. For instance, a cell such as we use on street cars gave a
useful capacity of 137.3 ampere hours when discharged at the average
rate of 45.76 amperes, and this same cell yielded 156.38 ampere hours
when worked at the rate of 22.34 amperes. At the commencement of the
discharge the E.M.F of the battery was 2.1 volts, and this was allowed
to drop to 1.87 volts when the experiment was concluded. The entire
active material contained in the plates of one cell weighed 11.5 lb.,
therefore the energy given off per pound of active substance at the
above high rate of discharge was 62.225 foot pounds, and when
discharging at the lower rate of 22.34 amperes the available useful
energy was 72.313 foot pounds, or nearly 2.2 electrical horse power
per pound of active matter. But this active substance has to be
supported, and the strength or weight of the support has to be made
sufficiently great to give the plate a definite strength and
durability. The support of the plates inclusive of the terminals above
referred to weighs more than the active material, which consists of
peroxide of lead and spongy lead; so that the plates of one cell weigh
actually 26.5 pounds. Add to this the weight of the receptacle and
acid, and you get a total of about 41 pounds per cell when in working
order. Seventy of these cells will propel an ordinary street car for
four hours and a half, while consuming the stored energy at the rate
of 30 amperes, or over 5.6 electrical horse power. The whole set of
seventy cells weighs 2,870 lb., which is barely one-fifth of the
entire weight of the car when it carries forty adult passengers.
Therefore the energy wasted in propelling the accumulator along with a
ear does not amount to more than 20 per cent. of the total power, and
this we can easily afford to lose so long as animal power is our only
competitor. From numerous and exhaustive tests with accumulators on
cars in this country and abroad, I have come to the conclusion that
the motive power for hauling a full-sized street car for fifteen hours
a day does not exceed $1.75, and this includes fuel, water, oil,
attendance, and repairs to engine, boiler, and dynamo. We have thus an
immense margin left between the cost of electric traction and horse
traction, and the last objection, that relating to the depreciation of
the battery plates, can be most liberally met, and yet leave ample
profits over the old method of propulsion by means of animals.
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