The subject of secondary batteries has been so ably treated by Professor
Silvanus Thompson and Dr. Oliver Lodge, in this room, that I should
vainly attempt to give you a more complete idea of their nature. The
improvements which are being made from time to time mostly concern
mechanical details, and although important, a description will scarcely
prove interesting.
A complete Faure-Sellon-Volckmar cell, such as is used in the existing
electric launches, is here on the table; this box weighs, when ready
for use, 56 lb.; and it stores energy equal to one horse power for one
hour=1,980,000 foot pounds, or about one horse power per minute for each
pound weight of material. It is not advantageous to withdraw the whole
amount of energy put in; although its charging capacity is as much as
370 ampere hours, we do not use more than 80 per cent., or 300 ampere
hours; hence, if we discharge these accumulators at the rate of 40
amperes, we obtain an almost constant current for 71/2 hours: one cell
gives an E.
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