of Contents]People old and young enjoy waxing nostalgic about and learning some of the history of early electronics.
Popular Electronics was published from October 1954 through April 1985. As time permits, I will be glad to scan articles
for you. All copyrights (if any) are hereby acknowledged.
"Mr. Scott, prepare to
load the promethium batteries into the
chamber." OK, I made up the promethium batteries part, but you might not have suspected it. Back in the mid to
late 1950s, atomic batteries were seriously thought to potentially (no pun intended) be a futuristic source of
energy storage and generation. The concept worked by having beta particles from promethium decay impinge on
silicon photodetectors, and having that be the source of power. That's almost as Rube Goldbergish as having a
gasoline engine drive an electric generator to power a motor for automotive locomotion. Oh, wait, that describes
the Chevy Volt.
Note that in 1959, nickel cadmium (NiCad) batteries were just coming into commercial use,
and the author envisions a day when they might be used for portable power tools and flashlights. At least he was
right about that one.
See the 1957 edition of Time magazine with an article titled, "Science:
New Atomic Battery
See all articles from
Recent Developments in Battery Design
Atomic batteries, fuel cells, and other new battery types hold great promise for the future
by Saunder Harris, WINXL
soldiers at a front-line observation post crouch behind a strange-looking device that looks like a spotlight: As
they wait in the darkness, instead of straining their eyes to discern enemy movements, their attention is riveted
to the spotlightlike device. Capable of spotting a single enemy soldier a half-mile away in total darkness, this
is the Army's new "Silent Sentry" mobile radar set.
. Operation of the fuel cell. Electron flow from hydrogen electrode to oxygen electrode
provides electric current.
who did much of the research on the fuel cell, Dr. Karl Kordesch, examines an
electrode used in the cell.
and mercury batteries such as these are already on the market.
. Exploded view of mercury battery (courtesy National Carbon Company)
. Comparison of discharge curves of mercury cell and carbon-zinc cell. It is readily seen
that the mercury cell enjoys a much longer useful service life.
. Typical simple rectifier circuit employed to reactivate rechargeable batteries.
. Promethium cell composed of center layer of promethium and phosphor with outer layers
made up of photocells.
Under battle conditions quiet operation of the Silent Sentry could be a matter of life or death; therefore, a
noiseless source of power for the unit is essential. Obviously, here is a job tailor-made for batteries. But which
type should be used? Of a whole parade of new batteries, the Army has chosen one of the newest-the little-known
fuel cell-to power the Silent Sentry.
The fuel cell is only one of the new battery types which are today
proving their worth. Already on the commercial market are the tiny, power-packed mercury cell and the rechargeable
nickel-cadmium battery. Before long, the fuel cell, too, will be available to private citizens. And the most
fascinating development in batteries - the amazing promethium cell which is powered by energy from the atom itself
- is now being tested and refined in research laboratories in this country.
Let's examine these "wonder" batteries. First, since it's one of the newest, we'll take a look at the fuel
cell, the power source of the Silent Sentry.
. The most interesting characteristic of the fuel cell is that, unlike conventional
batteries, it never becomes exhausted. Since it produces electrical current from the electrochemical reaction
which takes place when oxygen and hydrogen are combined, the fuel cell itself remains usable as long as the "fuel"
- oxygen and hydrogen - is supplied.
Operation of the fuel cell is diagrammed in Fig. 1. Oxygen and hydrogen enter the cell through two hollow
carbon electrodes. Since these electrodes are porous, the gases rapidly diffuse to the outer surface of the
electrodes where they come into contact with the electrolyte, a solution of potassium hydroxide. The chemical
reaction which takes place releases electrons from the hydrogen electrode which flow through the external circuit
and are returned at the oxygen electrode. It is this flow of electrons which provides the electric current. Water,
a by-product of the reaction, is passed from the cell in the hydrogen stream.
One fuel cell can produce
only about one volt. Any required voltage may be attained, however, by simply connecting the cells together in
series. As with ordinary dry cells, the amount of current which can be drawn from a fuel cell is a function of its
physical size. Thus, by varying the number and size of the cells, many variations of voltage and current can be
obtained. Fuel cells have been operating eight hours a day, five days a week, for over a year with no sign of
It is very possible that the fuel cell will be the practical means of putting both nuclear
energy and solar energy to use. At present, one of the big difficulties involved in using the energy of the sun is
in storing its power for future use. Now, during the sunlight hours, the sun's energy could be used to decompose
water, producing both hydrogen and oxygen for later use in fuel cells. In the same manner, where nuclear reactors
are used as heat sources in steam generating plants, the nuclear energy decomposes water. Instead of this being a
disadvantage, as it has been, this process can now be the means of producing the necessary hydrogen and oxygen for
fuel cell operation.
. Wherever long life and lots of punch must be jammed into a small package, the
mercury battery has come into wide use. This battery was developed primarily for hearing aids and other
An exploded view of a typical mercury battery is shown in Fig. 2. The materials
used in its construction are high-purity zinc powder for the anode, mercuric oxide and carbon for the cathode, and
potassium hydroxide as the electrolyte. The mercury cell develops an open-circuit voltage of approximately 1.35
Figure 3 illustrates the difference in performance between the mercury cell and the standard
carbon-zinc cell. It can be readily seen that the voltage of the mercury cell remains constant over a longer
period of time than does the carbon-zinc cell.
For general use, the mercury battery is very expensive. The
size "D" mercury battery (flashlight size) costs about $2.50 as compared with a price of 20 cents for an ordinary
carbon-zinc "D" cell. This high cost is due to the expensive materials used in construction. Mercury batteries
became financially practical only when devices such as hearing aids were designed to use them.
. Along with other dry cells, the mercury battery suffers from one big
disadvantage. It cannot be recharged. However, rechargeable nickelcadmium batteries are just coming into popular
use today in rechargeable flashlights, radios and electric razors. Tomorrow they may be used to power TV sets,
portable electric drills, and perhaps even your car.
After conventional dry cells have been used awhile,
the action of the cell is gradually choked off by a gas which is developed in the cell. In the nickel-cadmium
battery, the recharging process converts this gas back into a liquid, thus reactivating the cell. Recharging is
accomplished by plugging the battery unit into the house power line. Figure 4 shows a typical half-wave rectifying
circuit used for this purpose. In most cases, the rectifier is built into the same unit as the battery.
Nickel-cadmium cells can't give you something for nothing, however. Rechargeable cells cost more, and give
less energy per charge than an ordinary carbon-zinc cell. For example, a nickel-cadmium flashlight cell costs
about $2.75 as against 20 cents for a comparable carbon-zinc cell. But it can be charged over and over.
Even more expensive than the nickelcadmium battery is its highly refined "cousin," the silver-cadmium battery.
This battery enjoys all the advantages of the nickel-cadmium design, and, in addition. offers higher output at
one-half to onethird its size and weight. Since the silvercadmium battery is quite costly, its greatest
application so far has been in rockets. missiles, and satellites. Atomic Batteries
misleading publicity has surrounded the atomic battery. In spite of newspaper reports which would lead you to
believe that an atomicpowered radio is just around the corner this is not the case. As one battery engineer put
it, "there are a great many problems to be solved before atomic batteries are brought out of the laboratories and
put into your home."
One objection to the atomic battery i its potential danger. How would you like to
have a little package of radioactivity around the house where it might be broken into by youngsters with a yen for
experiments? Another objection is cost; at this time, the material which goes into such batteries is extremely
expensive, The batteries we have working for us now do a good job at reasonable cost and the idea of replacing
them with atomic batteries might be novel but cannot be considered practical at present .
laboratory research continues on the atomic battery. Radioactive promethium - promethium is a by-product of
uranium fission - is the power source. It is valuable because it emits large amounts of beta rays (actually
electrons) over its 2 1/2-year half-life. These beta rays can be tapped as a source of power. Alpha a gamma rays
are emitted only in small quantities.
The actual size of the promethium and its shielding is about that of a penny Figure 5 shows a typical promethium
cell in cross section. The center layer is a mixture of promethium and phosphor. Small photocells compose the
outer layers. When the promethium gives off beta rays, they strike the phosphor with great force. The phosphor
then lights up in much the manner as your TV screen does when the electron stream of the cathode-ray tube hits it.
This light is then converted to electrical energy by the two outer layers of photocells.
Output of the
promethium cell is small actually less than one-millionth of the electrical power used by a 40-watt bulb. It
does give off power, though, and the power comes from atomic radiation. Considering its early stage of
development, the promethium cell shows great promise.
Any discussion of batteries must necessarily lead us
back to the fact that the carbon-zinc cell is still battery king of the present. And in the distant future, when
you send one of the kids down to the Lunar Hardware on the Moon to pick up a battery for your flashlight, chances
are you will end up with our old friend, the carbon-zinc cell. Posted