[Footnote 1: From a paper read before the National Electric Light
Association, New York, August, 1887.]
By A. RECKENZAUN.
The idea of employing secondary batteries for propelling vehicles is
almost contemporaneous with the discovery of this method of storing
energy. To Mr. Plante, more than to any other investigator, much of
our knowledge in this branch of electrical science is due. He was the
first to take advantage of the action of secondary currents in voltaic
batteries. Plante is a scientist of the first grade, and he is a
wonderfully exact experimenter. He examined the whole question of
polarization of electrodes, using all kinds of metal as electrodes and
many different liquids as electrolytes, and during his endless
researches he found that the greatest useful effect was produced when
dilute sulphuric acid was electrolyzed between electrodes of metallic
lead.
A set of Plante's original cells was exhibited for the first time in
March, 1860, before the Paris Academy of Sciences. Scientists admired
and praised it, but the general public knew nothing of this great
discovery thus brought to notice. Indeed, at that period little
commercial value could be attached to such apparatus, since the
accumulator had to be charged by means of primary batteries, and it
was then well known that electrical energy, when produced by chemical
means in voltaic cells, was far too expensive for any purpose outside
the physical laboratory or the telegraph office.
It was twenty years after this exhibition at the Academy of Sciences
in Paris that public attention was drawn to the importance of storage
batteries, and that Mr. Faure conceived the idea of constructing
plates consisting of lead and oxides of lead. At that time the
advantages accruing through a system of electrical storage could be
fully appreciated, since electrical energy was already being produced
by mechanical means through the medium of dynamo-electric machines.
It was the dynamo machine which created the demand for the storage
battery, and the latter was introduced anew to the public at large
and to the capitalist with great pomp and enthusiasm. One of Faure's
accumulators was sent to Sir William Thomson, and this eminent
scientist in the course of experiments ascertained that a single cell,
weighing 165 lb., can store two million foot-pounds of energy, or one
horse power for one hour, and that the loss of energy in charging did
not exceed 15 per cent. These results appeared highly encouraging.
There we had a method of storing that could give out the greater part
of the energy put in. The immense development which the electric
transmission of energy was even at that early day expected to undergo
pointed to the fact that a convenient method of receiving large
quantities of transmitted energy, and of holding it in readiness until
wanted, must be of the highest importance. Numerous applications of
the Faure battery were at once suggested, and the public jumped to the
conclusion that a thing for which so many uses could be instantly
found must necessarily be a profitable investment, and plenty of money
was provided forthwith, not with the idea of commencing careful
experiments and developing the then crude invention, which would have
been the correct thing, but for manufacturing tons of accumulators in
their first and immature form.
I need not describe the disappointments which followed the first
unfulfilled hopes, nor repeat the criticism that was heaped upon the
heads of the early promoters. Those early hopes were untimely and
unreasonable. A thousand difficulties had to be overcome--scientific
difficulties and manufacturing difficulties. This invention, like most
others, had to go through steady historical developments and
evolution, and follow the recognized laws of nature, which are against
abnormal and instantaneous maturity. The period of maturity has also
been retarded by injudicious treatment, but the ultimate success was
inevitable. Great advances have been made within the last few years,
and I propose now to offer a few facts and figures relating to the
present state of the subject with reference to the application of
storage batteries to locomotive purposes. It is not within the
province of this paper to discuss all the different inventions of
secondary batteries nor to offer any suggestions with regard to
priority, therefore I will confine myself to general statements. I am
aware of the good work that was done in the United States by Kirchhoff
twenty-six years ago, and of the more recent work of Mr. Brush, of
Cleveland, Mr. Julien and others, but I am more particularly
acquainted with the recent achievements of the Electrical Accumulator
Company, who own the rights of the Electrical Power Storage Company,
of London. I have used the batteries of the latter company for
propelling electric boats and electric street cars. The first of the
boats was the Electricity, which was launched in September, 1882, and
which attained a speed of seven miles an hour for six consecutive
hours. Since then a dozen electric boats of various sizes have been
fitted up and worked successfully by means of storage batteries and
motors of my design. The most important of these were the launch Volta
and another similar craft, which is used by the Italian government for
torpedo work in the harbor of Spezia. On the measured mile trial trips
the Italian launch gave an average speed of 8.43 miles an hour with
and against the tide. The hull of this vessel was built by Messrs.
Yarrow & Co., and the motors were manufactured by Messrs. Stephens,
Smith & Co., of London. The Volta, which was entirely fitted by the
latter firm, is 37 feet long and 7 feet beam. She draws 2'6" of water
when carrying 40 persons, for whom there is ample sitting
accommodation. There are 64 cells in this boat. These are placed as
ballast under the floor, and actuate a pair of motors and a screw
coupled direct to the armature shaft running at 700 revolutions a
minute. We crossed the English Channel with this boat in September of
last year, leaving Dover at 10:40 in the morning, arriving at Calais
at 2:30 P.M.; stayed about an hour in the French harbor for luncheon
and floated into Dover docks the same evening, at 6:30, with full
speed. The actual distance traversed without entirely discharging the
cells was 54 miles. The current remained constant at 28 amperes until
5 P.M., and it only dropped to 25 amperes at the completion of the
double voyage between England and France. Several electric launches
are now being constructed in London, and one in New York by the
Electrical Accumulator Company.
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 1¼ 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.
The advantages of storage battery street cars for city traffic are
self-evident, so that I need not trouble you with further details in
this respect, but I would beg those who take an interest in the
progress of the electric locomotive to give this subject all the
consideration it deserves, and I would assure them that the system
which I have advocated in this brief but very incomplete sketch is
worthy of an extended trial, and ready for the purposes set forth.
There is no reason why those connected with electric lighting
interests in the various cities and towns should not give the matter
their special attention, as they are the best informed on electrical
engineering and already have a local control of the supply of current
needed for charging.
In the car which we use in Philadelphia there are actually 80 cells,
because there are considerable gradients to go over. Each cell weighs
40 pounds and the average horse power of each battery is six.
Sometimes we only use two horse power and sometimes, going up grades
of 5 per cent., we use as much as 12 horse power, but the average rate
is 6 electrical horse power. With reference to the weight of
passengers on the cars, we have never carried more than 50 passengers
on that car, because it is impossible to put more than 50 men into it.
There are seats for 24, and the rest have to stand on the platforms or
in the aisle.
The changing of the batteries takes three minutes with proper
appliances. One set of cells is drawn out by means of a small winch
and a freshly charged set is put in. It takes the same time to charge
the battery as it does to discharge it in the working of the cars, so
one reserve set would be sufficient to keep the car continually
moving.
The loss of energy from standing about is probably nothing. If a
battery were to stand charged for three months in a dry case, the loss
of energy might be in three months 10 per cent. I purposely had a set
of cells standing for two years charged and never used them. After two
years there was still a small amount of energy left. So as regards
the loss of energy in a battery standing idle, it is practically
nothing, because no one would think of charging a battery and letting
it stand for three months or a year.
I have had them stand three or four months and I could hardly
appreciate the loss going on, provided always that the cells are
standing on a dry floor. If the exterior of the box be moist, or if it
stands on a moist floor, there will naturally be a surface leakage
going on: but where there is no surface leakage the mere local action
between the oxides and metallic lead will not discharge the battery
for a very considerable time.
I have made experiments in London with a loaded car pulled by two
horses. I put a dynamometer between the attachment of the horse and
the car, so as to ascertain exactly the amount of pull, measured in
pounds multiplied by the distance traversed in a minute. You will be
surprised to know that two horses, when doing their easiest work,
drawing a loaded car on a perfectly level road, exert from two to
three horse power. I have mentioned a car in Philadelphia where we use
between two and twelve horse power. A horse is capable of exerting
eight horse power for a few minutes, and when a car is being driven up
grades, such as I see in Boston, for instance, pulling a load of
passengers up these grades, the horses must be exerting from 12 to 16
horse power, mechanical horse power. That is the reason that street
car horses cannot run more than three or four hours out of the
twenty-four. If they were to run longer, they would be dead in a few
weeks. If they run two hours a day, they will last three or four
years.
The life of the cells must be expressed upon the principle of ampere
hours or the amount of energy given off by them. Street car service
requires that the cells work their hardest for fifteen or sixteen
hours a day. The life of the cells has to be divided; first, into the
life of the box which contains the plates. This box, if appropriately
constructed of the best materials, will last many years, because there
is no actual wear on it. The life of the negative plates will be very
considerable, because no chemical action is going on in the negative
plate. The negative plate consists almost entirely of spongy lead, and
the hydrogen is mechanically occluded in that spongy lead. Therefore
the depreciation of the battery is almost entirely due to the
oxidation of the positive plates. If we were to make a lead battery of
plates ¼ inch thick, it would last many years; but for street car
work that would be far too heavy. Therefore we make the positive
plates a little more than one-eighth of an inch thick. I find that the
plates get sufficiently brittle to almost fall to pieces after the car
has run fifteen hours a day for six months. The plates then have to be
renewed. But this renewal does not mean the throwing away of the
plates. The weight is the same as before, because no consumption of
material takes place. We take out peroxide of lead instead of red
lead. That peroxide, if converted, produces 70 per cent. of metallic
lead, so that there is a loss of 30 per cent. in value. Then comes the
question of the manufacture of these positive plates, which, I
believe, at the present day are rather expensive. But I believe the
time will come when battery plates will be manufactured like shoe
nails, and the process of renewing the positive plates will be a very
cheap one.
I ascertained in Europe that the motive power costs 2 cents per car
mile; that is, the steam power and attendance for charging the
batteries. We have to allow twice as much for the depreciation of a
battery at the present high rate at which we have to pay for the
battery--$12 for each cell. But I believe that as soon as the storage
battery industry is sufficiently extended, the total cost for
propelling these cars will not be more than six cents a mile, or about
one half the cost of the cheapest horse traction.
I have made some very careful observations on the cable tramway in
Philadelphia, which is quite an extensive system. I have never been
able to ascertain the exact amount of waste in pulling the cable
itself; but I have it on the authority of certain technical papers
that there is a waste of about eighty per cent. I do not intend to
depreciate cable or any other tramways, but there is a difficulty
about introducing cable tramways. It is necessary to dig up the
streets and interfere with the roadways. I have been told that the
cable arrangements in Philadelphia cost $100,000 a mile, and that the
cable road in San Francisco cost more than that. One of the directors
of the cable company in Philadelphia told me that if he had seen the
battery system before the introduction of the cable, he would probably
have made up his mind in favor of the former. The wear and tear in the
case of the storage system is also considerable. There is a waste of
energy in the dynamo; secondly, in the accumulator charged by that
dynamo; thirdly, in the motor which is driven by the accumulator; and
fourthly, in the gearing that reduces the speed of the motor to the
speed required by the car axles. It would be difficult to make a motor
run at the rate of eighty revolutions per minute, which is the number
of revolutions of the street car axle when running at the rate of ten
miles an hour. Take all these wastes, and you find in practice that
you do not utilize more than 40 per cent. of the energy given by the
steam engine. But this is quite sufficient to make this system much
cheaper than horse traction.
It is well known that we can discharge the storage battery _ad
libitum_ at the rate of 2 amperes or 200 amperes. I can get out of a
storage battery almost any horse power I like for a short space of
time. I have not the least objection to the direct system. But when
you come to run twenty or thirty or fifty cars on one line, you will
require very large conductors or dangerously high electromotive force.
The overhead system is applicable to its own particular purposes.
Where there are only five or ten, or even twenty, cars running on one
line, and that line runs through a suburb or a part of a city where
there are not many houses, that system is to be preferred. The
objection to the overhead system is not so much the want of beauty,
but the want of practicability. You have to put your posts very high
indeed, so as to let great wagon loads of hay and all sorts of things
pass underneath. Most of the trouble comes in winter, and when it is
snowing hard a great many difficulties arise. As regards the loss,
suppose that the resistance of the overhead lines is one ohm. To draw
one car it will take an average of 20 amperes, and the only loss will
be 20 multiplied by 20, that is, 400 watts through line resistance.
But if there are ten cars on that line, you get 40,000 watts loss of
energy, unless you increase the conductor in proportion to the number
of cars. If you do that, you get an enormous conductor, and have a
sort of elevated railroad instead of a telegraph wire, as most people
imagine an overhead conductor to be.
The current required to run a street car is about thirty amperes, and
an electromotive force of about 180 volts. If cars are run in
connection with an incandescent light station, we can arrange our
apparatus so that we can use an E.M.F. say of 110 volts, and then we
can put in a smaller number of cells with a larger capacity that will
give a corresponding horse power. We can charge such larger cells with
50 or 60 amperes instead of thirty.
In regard to arc lighting machinery, the arc lighting dynamo should
not be used to charge the accumulators. They can be used, but they
require such constant attention as to make them impracticable. We can
only use shunt-wound dynamos conveniently for that purpose.
In regard to using two motors on a car, there are several advantages
in it. I use two motors on all my cars in Europe, and always have done
so from the beginning. One of the advantages is that in case of an
accident to one motor the other will bring the car home; secondly,
with two motors we can vary the speed without changing the E.M.F. of
the battery. If I want very much power, I put two motors in parallel,
getting four times the power that I do with one machine, and an
intermediate power of two motors.
There is another advantage of having two motors, and that is that we
can use two driving axles instead of one, and we can go up grades with
almost double the facility that way, because the adhesion would be
double. These are the main advantages arising from the use of two or
more motors.
Mr. Mailloux asked if I would give my experience in regard to the
mechanical transmission between the motor and the car axle. I have
used almost everything that was known at the time, but in order to
give you a full and detailed account of the various modes of
transmission which I have used I should have to give you figures to
bear out certain experiments. I should only be able to do that in a
lecture of at least five hours' duration, so I hope that you will
kindly excuse me on that point.
With regard to the durability of plates, I have taken into
consideration fifteen hours a day. In regard to the application of
electrical brakes, I will say that that was one of the first ideas
that entered my head when I began to use electric motors, and other
people had that idea long before me. I have used an electric brake,
using the motor itself as a brake--that is, as the car runs down a
grade by momentum, it generates a current, but this current cannot be
used for recharging a battery. It is utter nonsense to talk about that
unless we have a steady grade four or five miles long. The advantages
are very small indeed, and the complications which would be introduced
by employing automatic cut-outs, governors, and so on, would
counterbalance anything that might be gained. As regards going up an
incline, of course stopping and starting again has to be done often,
and anybody who at any time works cars by electricity, whether they
have storage batteries or not, has to allow for sufficient motive
power to overcome all the difficulties that any line might present.
One of the great mistakes which some of the pioneers in this direction
made was that they did not put sufficient power upon the cars. You
always ought to put on the cars power capable of exerting perhaps 20
to 40 per cent. more than is necessary in the ordinary street service,
so that in case of the road being snowed up, or in the case of any
other accident which is liable to occur, you ought to have plenty of
power to get out of the scrape.
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