Momentum - February 2020 - 15

TODAY'S

ENGINEERING

CHEVY TWEAKS 2020 BOLT'S
BATTERY CHEMISTRY TO ADD RANGE
IN LATE 2016, the Chevrolet Bolt became
a breakthrough vehicle for long-range EV
affordability. At the time, no other electric
car came close to offering the Bolt's 238
mi (383 km) of driving range at a base
price of about $37,000. But since then,
GM saw the Bolt's lead surpassed by the
Tesla Model 3, by far the best-selling EV
in recent years. The base Model 3 nearly
matches the Bolt's price, while offering
the same range, high-tech features, and
faster charging. In 2018, the Hyundai Kona
Electric was rated for 258 miles (415 km)
of range, claiming long-range supremacy
among EVs selling for below $40,000.
Facing competition, two years ago GM
started a conversation with LG Chem, the
Bolt's battery supplier, about what could
be done. The automaker challenged the
South Korean battery-maker to find a
way to increase the range of the Bolt's
60-kwh battery, aiming for a 10% bump.
LG Chem proposed several options,
according to YoungNam Kim, a battery
cell technical specialist for GM. "They
said the easiest way would be to make
a brand-new cell for GM," Kim said. But
GM's vehicle engineering team didn't
want to alter the battery pack or its
packaging in the vehicle.

BETTER LIVING THROUGH
CHEMISTRY
After more than a year of discussions in
which both LG Chem and GM conducted
tests of new chemistries, the teams
settled on a new recipe. Chevrolet
announced on August 22, 2019, that the
2020 Bolt had earned an official EPA
range of 259 mi (416.8 km). It has 66 kW
of usable battery capacity.
On the eve of the first media drive of
the 2020 Bolt, Kim held up two battery
cells, one from the outgoing 2019 Bolt
and the new-and-improved version. They
looked nearly identical. "The length of
the cells is exactly the same. The width
and thickness are slightly different," Kim
said, noting there are about 100 layers of
anode, cathode, and separator.
MOMENTUM

We charged at 53 KW for 20 minutes at the Three Rivers Mall station in Keslo, Wash. Our car is the
blue one.
Robert Mantinan, engineering manager,
explained: "It has the same number
of cells, the same enclosure, the same
format, and the same layout." GM declined
to disclose the new battery recipe for the
2020 Bolt pack, other than that it remains
a blend of nickel, cobalt, and manganese.
GM also said that the cells have additional
active material in the anode and cathode.
In recent years, automakers producing
electric vehicles have been trying to
increase the percentage of nickel in its
formulas, a strategy to improve energy
density. At the same time, reducing
the amount of cobalt reduces cost and
mitigates price volatility. Also, human
rights organizations have raised ethical
concerns about the use of child labor
to extract cobalt in the Democratic
Republic of Congo and other regions.
Cobalt and manganese help maintain cell
stability and long cycle life, extending the
reliability and longevity of EVs.
GM also used new methods for battery
lab testing, allowing the company to
lower the battery's resistance during
dc quick charging. "We optimized our
charging algorithms," Mantinan said.
The Bolt can now add 100 miles (160.9
km) of range in the first 30 minutes of
charging if the battery is nearly depleted
when starting a charging session, and the
ambient temperatures are mild.

YOUR MILEAGE MAY VARY
The 2020 Bolt's extra 21 mi (34 km) of
range and its ability to quickly add miles

via a dc fast charger proved critical during
our recent 240-mile (386-km) test drive.
To test the range, Chevrolet set a winding
course for journalists to travel from
Tacoma, Wash. to Portland, Ore. A day
earlier, engineers from GM successfully
completed the route. But that was under
sunny skies and 70°F (21°C) weather. By
the next day, the weather turned, and we
experienced long periods of pelting rain.
The temperature had dropped to about
45°F (7°C), prompting use of the cabin
heater. According to the Bolt's dashboard
indicator, the use of climate settings
reduced range by about 8%.
By the time we traveled 153 mi (246
km) to Astoria, Ore., we had used 47 kw∙h
of energy. The dashboard's estimated
remaining range was 59 mi (94.9 km),
not enough to complete the remaining
90 miles (144.8 km) to Portland. Among
the group of about 10 vehicles on the
media drive, one light-footed driver
arrived in Astoria with 100 mi (160.9 km)
of remaining range. The most aggressive
journalist had drained the battery down to
its last 15 mi (24 km) of estimated range.
The hard rain and wet road conditions
diminished the efficiency, requiring
that we make an electric pitstop at
the Electrify America DC fast-charging
location in Kelso, Ore.
(A longer version of this article can be
found on the SAE website.)

By Bradley Berman, U.S. West Coast Editor,
Automotive Engineering

February 2020 15

Momentum - February 2020

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