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January 1967 Popular Science
 [Table of Contents]
Wax nostalgic about and learn from the history of early
electronics. See articles from
Popular
Science, published 1872-2021. All copyrights hereby acknowledged.
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According to Wikipedia,
"A sodium-sulfur
(NaS) battery is a type of molten-salt battery that uses liquid sodium and
liquid sulfur electrodes. This type of battery has a similar energy density to
lithium-ion batteries, and is fabricated from inexpensive and low-toxicity
materials." They have a high operating temperature (300-350 °C), with energy
density of 300-400 Wh/L. That was the type battery planned for use by Ford in an
electric vehicle (EV). General Motors, in this case, had "A
Better Idea:" an EV version of its compact Corvair car, aka the Electrovair,
per this 1967 Popular Science magazine article. It was to be powered by
a silver-zinc
battery (325-375 Wh/l). The concept never took off, as history has shown, but
the reason was probably more due to inferior brushed DC motor technology
compared to modern brushless motors with supermagnets and multi-phase,
microprocessor-controlled driver circuits, than to battery technology. Li-Po
batteries have slightly greater energy density than the other two types, but are
cheaper to build and exhibit superior charging and discharging properties. Time
will tell whether EVs are universally desired by motorists, or dominate
production due to government mandates in spite of any true net ecological
benefit - like what happened with compact fluorescent lamps (CFL).
GM Makes an Electric Corvair
 PS Detroit Editor Dunne looks over car's forward batteries. Tires are oversize
to carry added weight.
Recently the Ford Motor Co. announced the development of a sodium-sulfur battery
that could power a production-line electric car, perhaps within five years [PS,
Dec. '66]. Now General Motors has gone Ford one better - it has exhibited an experimental
electric driven by a silver-zinc battery.
Jim Dunne, PS Detroit editor, is the only person apart from GM personnel to have
driven it. Here are his comments:
"You flip the ignition switch to ON. No sound. A needle on the battery voltage
dial swings up. That's your power indication. A blower for an oil cooler whirs -
oil is used to keep down the temperature of the motor and controls. The high currents
involved produce a lot of heat.
"You shift a lever to D-for-drive to put the car in gear. There's no gear shifting,
of course. You press the accelerator. Not all the way, a GM engineer beside you
warns - just enough to get rolling. Initial acceleration is slow. Once you're going
five m.p.h., you can floor it.
"Zero to 60 takes 16 seconds in this vehicle, built on a Corvair chassis and
named the Electrovair II. The only sound besides the blower is a buzz, pitched low,
then high as you gain speed. The handling is imprecise. Heavier than a standard
Corvair by 800 pounds, the car wallows.
"The performance is smooth, though. Top speed is 80 with the motor at 15,000
r.p.m. That's just for spurts. Motor speed for normal driving is redlined at 13,000
or 60 m.p.h."
The Electrovair II has other debits, and on the basis of Ford's projections for
its car, GM will have to hump to compete. GM's batteries alone cost $15,000, controls
$5,000, chassis $1,000. That's now. If the car ever got into production, costs might
toboggan. Both the front and rear compartments are loaded with batteries and machinery
weighing 1,230 pounds.
Electrovair II is driven by a three-phase AC induction motor.
It weighs only 1.3 pounds per horse-power. Switching equipment changes batteries'
direct current to alternating current. It varies both the voltage and frequency
of the power. This unit requires 18 silicon-controlled rectifiers to handle the
high currents in the short switching time available at 13,000 r.p.m. Since switches
can be turned on but not off by a small power pulse, car requires a set of capacitors,
which are alternately charged and discharged to blow the switches out. Second block
of capacitors is needed to smooth out power flow to motor. A "logic box" translates
driver's control from ignition switch, gear lever, and accelerator into signals
to develop more power, less power, or motor reversal. It also contains a series
of safety circuits. Ordinary lead-acid battery, driven by motor, supplies current
for lights, heater, and horn.
The complete stopper at present is that the batteries wear out after 100 recharges.
Ford says its batteries should be good for the life of the vehicle.
There are credits. The Electrovair II, like the proposed Ford electric, emits
no gases to foul the air. The batteries recharge in six hours on ordinary house
current. With a full charge, the car will go 40 to 80 miles, depending on the speed
at which it's driven.
GM figures a production electric car is at least 10 years away.
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