Shift Magazine - July 2021 - 22

last mile
For the first EV
owners, charging
at home was a
dangerous
proposition
An early-1900s electric automobile
with a mercury arc rectifier,
once used to charge EVs.
Museum of Innovation and Science
BY RICHARD TRUETT
S
ome aspects of modern electric
vehicle ownership have not
changed much from the first generation
of EVs that were popular
a century ago. Back then, as today, there
was range anxiety. Part of that was borne
out of the charging situation.
Back then there were three ways to
charge electric car batteries:
1. The vehicle could be left at the dealership
overnight.
2. The battery pack could be removed and
replaced with a freshly charged pack.
3. The vehicle could be plugged into one
of the few public charging stations.
Home charging also was possible,
but it was not widespread. The charging
22 shift * july 2021
equipment was expensive and not very
user-friendly like today's chargers. Because
of exposed wiring and mercury arc rectifiers,
a battery charger could be dangerous
to have in a home garage, where it may not
be shielded well from moisture and could
be damaged easily if something banged in
to it.
A mercury arc rectifier converts AC
power from the grid to DC power for a
vehicle's battery pack. The rectifier -
which looks like something from a Flash
Gordon movie - contains a pool of liquid
mercury in a glass tube that has at least
three electrodes.
When electricity from the grid is applied
to the mercury, which acts as a cathode,
it is vaporized and creates an arc that
releases electrons that travel to the anode
to create direct current.
Solid-state technology in the 1960s
began replacing mercury arc rectifiers,
and the last ones, used by the New York
subway system, were retired in the 1990s.
General Electric took what may be the
first shot at public charging stations with a
device called the Electrant (short for electric
hydrant). The devices were used in
New York and other large cities to recharge
the battery packs in electric taxi cabs.
Although there were about 43,000
public charging stations in the U.S. as
of July 1, according to the Department
of Energy, recharging a depleted pack
takes plenty of time, same as it did a century
ago. According to charging network
Electrify America, up to 80 percent of EVs
today are charged at home. n
Shift Magazine - July 2021

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