The
Edison
Cell
By Walter Noon III
With the wild fluctuations in fuel
prices over the last few years, world
concern over global warming, and
simply the idea of creating new and
more sustainable technologies,
immense interest and progress has
developed recently in the world of
battery development.
In fact, it seems that every day we hear of a new breakthrough, and another step closer to that long sought elusive goal of a truly workable battery
storage system! Perhaps one day soon we’ll have a battery
that displays no “memory” effect, one that can be
completely discharged or overcharged without harm, and
require no complex computerized management system.
This battery could even prove so durable it will be
immune to damage from vibration and not break down
chemically over time. In operation, such a battery might
even routinely outlast the very vehicle or machine it was
designed to operate in! Last, we could complete our wish
list by adding in the impossible: low materials toxicity,
simple construction, and, of course, good energy density.
Does such a battery sound like too much to hope for?
Thomas Edison didn’t think so when in 1899 —
working with a design pioneered by Waldemar Jungner —
he patented a battery with all these characteristics.
It was Edison’s hope that electric vehicles — which
currently had the lead in popularity — would easily trump
internal combustion or steam to be the vehicle of choice
of his time, and ours. The Edison cell had a greater energy
density than popular lead acid, and recharged in half the
time. Astoundingly, it was not harmed by being fully
discharged (even if dead shorted for years), and
overcharging occasionally was actually good for the cell. It
was even recommended as a monthly exercise in the
battery’s manual!
38 February 2012
Edison advertised that the cell had a life of at least
four years, but the materials proved to be so stable (due to
the low solubility of the reactants in the electrolyte) that
some are still producing their full capacity today after
more than 50 years! Problems with the Edison cell were
few, and included poor performance at low temperatures,
a high self discharge rate when unused (20% to 40% per
month), and a slower than normal charge and discharge
rate (65%). Yet, the practical nature of these cells was
undeniable, and perhaps remains so today.
Like many overlooked gems throughout the history of
engineering, perhaps these “diamonds in the rough”
deserve a second look and some thoughts as to how our
present technology could be improved by examining the
principles of their operation. Many times historically these
cells have been referred to as “the battery that worked too
well.” Though they were popular and profitable in niche
markets for Edison, it has been said that a business model
could never be created for the general public by producing
a product that does not require replacement. However,
these days where “going green” is more than a quaint idea,
perhaps Edison’s idea has finally found its time.
Constructing an
Experimental Edison Cell
Because I know first hand the ingenuity and depth of
knowledge of Nuts & Volts readers, I’d like to present the