Opinions from Others.
Page 19
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Battery v. Battery.
The Editor, THE COMMERCIAL MOTOR.
[1391] Sir,—In your recent article on "The Choice of a Battery" (11th February) there appear many inaccurate statements anent the Edison accumulator. It would, we consider, prejudice our interests if these inaccurate assertions remained uncorrected, and therefore we rely on the hospitality of your columns in order that we may rectify the errors in question. Firstly, we assert that no lead plate type of lead battery will give two years constant service—say 50 Miles per diem for 600 days. We know of only one make of lead battery that is guaranteed at all, and This is a tube type cell, warranted to give 80 per cent.. of original rating after two years work. There are no recorded instances of such cells giving an aggregate day after day service of 30,000 miles however. [The last paragraph of our "Choice of a Battery' article was as follows :—" To avoid the possibility of a misunderstanding of the above notes, it should be pointed out that, in referring to the lead-plate cell, we have in mind the modern and improved type, now in general use —for example, the Ironclad cell, which is of ,special tubular formation.—En.]
Secondly, the Edison accumulator is not in the slightest degree worn out by being left on open circuit. It is a special Edison feature that, unlike most lead cel's,ir-hich are greatly harmed by remaining quite unattended on open circuit, the Edison accumulator is worn out only by actual use. Even in continuous service the Edison accumulator is guaranteed to give full rated capacity after four years day-afterday service. [The form of guarantee published by Edison Accumulators, Ltd., reads as follows :--" If, at any time within a period of four years from the date of shipment, any of the cells are found to be incapable of developing full-rated capacity, etc."—Er.] Many -lahs will entail from 60 to 100,000 miles of ser-vice during this guarantee period, yet we know, from most extended laboratory and practical trials, that the chances of an Edison cell breaking down within this period are negligible. What counts in electric-vehicle service is a combination of 1igii ass, mechanical strength and simplicity of operation. The Edison cell is demonstrably the most advanced example of mechanical ruggedness in storage battery construction that has ever been achieved. Would any other commercially available
'• ever approach the results proved by the test of two Edison cells, which remained unharmed after being subjected to two million consecutive jolts on a shaking machine? Yet some standard Edison cells remained unimpaired after such severe treatment; that is, after an amount of mechanical energy equal to 1100 ft.-tons Of work had been expended in successively jolting them during their fortnight's ordeal on the shaking machine. Scientific tests indicate that in normal service the Edison cell will give its rated capacity after 3750 cycles of charge and discharge. Assuming only an average result of 2000 cycles, this would mean—taking an average figure of 45 miles per charge—a useful mileage life of 90,000 miles per battery, even then about six or seven times the average service life of a lead accumulator.
A practical, example hereanent is afforded by the results of some capacity tests made on Edison accuthulatora which, after five years service in the employ of the Adams Express Co. (a concern which has in service 800 Edison accumulator electrics) gave still 10 per cent, above their rated capacity. The distance covered was 40,000 -miles in parcel-delivery service.
By the way, you should know that constant veltage charging, as recommended by lead battery makers (at 2.3 volts per ceP) takes about 12 hours. This is not commercially allowable in most cases.
One last point! On page 477 of your issue of 25th February you state that Barnes U.D.C. has placed an order with us for four petrol-driven dust vans. For the information of the writer of that quaint announcement, let us state that we are interested only in pure electrics, the type that is equipped with the Edison accumulator. Naturally a petrol vehicle would not be equipped with accumulators, nor an accumulator vehicle with petrol gear.—Yours faithfully, For EDISON ACCUMULATORS, LirD., RAYMOND J. MITCHELL, Commercial Engineer.
[We express regret for misprint to which reference is made. The writer of the above letter surprises us in seeking to make any point out of an obvious slip. We refer on page 42 to the source of our information, and to a few broad considerations in the matter of battery-makers' claims and assertions.
Nobody seems to be able to ascertain what the Edison people will actually do under their guarantee on its termination at the end of four years; the uncertainty is no doubt, due to the fact that Edison Accumulators, La, has not once arrived at that stage yet. We will concede, after examin4tion of the company's quotations, that the maintenance of Edison batteries equals first cost once in each 5.8 (not four) years, at the best. This is considerably dearer than for certain lead-type batteries over the same period. As to
relative weights, the Edison equivalent of some standard lead batteries is almost identical. As to ratio of lead v. Edison in use, we did not confine ourself to Great Britain : we find the ratio for the U.S.A. (commercial vehicleg,) to he about 30 per cent. Edison and 70 per cent, lead, with perhaps only 10 per cent-Edison in private vehicles ; in Great Britain, quoting., from :the eurrent statistics which are -officially vouched by the Electric Vehicle Committee, we find (in use andon order, as they are -alone given), Edison batteries to be chosen for 143 vehicles and other battPries to be chosen for 337 vehicles.
Mr. Mitchell does not say anything about the low voltage at which the last 25 per cent, of the charge is obtainable, nor about the effect of winter temperatures upon the cells.—En.] A Substitute for Air.
The Editor, THE COMMERCIAL MOTOR.
[1392] Sir,—With regard to the interesting article on Rubberine Tire Fillings in your last issue, we think that there are one or two points in it which might be emphasized.
You state that "in the opinion of the company, difficulties which some other makers are finding are due to the fact that they have not discovered, the best temperature at which this material should be injected." It should be clearly understood that Rubberine is a proprietary patented article of a special nature, and that no "other maker" may produce it.
We also notice in one of your illustrations of a filled tire, that a shaded portion of the filling is shown and the note thereto states that "the darker portion shows later filling." Now, this not being referred to in the reading matter rather leaves the reader in the dark, but as this is an important feature of our process we should like to make the matter plain.
The illustration in question evidently shows a section of one of our filled tires which we gave to one of our motoring friends lately ; this ran for about 1500 miles on a car hawing a touring body ; the owner then had a limousine body built for the car, thus greatly increasing the weight and rendering the pressure at -which we originally filled the tires inadequate ; he then returned his two back wheels to us and we injected some more Rubberine into the tires, which, as the illustration shows, amalgamated perfectly with the original filling and so readily and permanently brought the pressure up to the required degree to stand the additional weight of the ear.
We may add that these tires afterwards ran for a further 6400 and 7200 miles respectively.—Yours
faithfully, RUBBERINE, LTD.