Automotive Engineering - February 2023 - 6

TECHNOLOGY
REPORT
BATTERIES
BMW readies move to structural batteries, '46120' cells
SAE INTERNATIONAL
BOARD OF DIRECTORS
Todd Zarfos
President
Carla Bailo
2024 President
Srinivasa (Sri) Srinath, Ph.D
2022 President
Susan Ying, Ph.D
Vice President - Aerospace
Daniel Nicholson
Vice President - Automotive
Audley Brown
Vice President -
Commercial Vehicle
Behind the BMW i Vision Dee's razzle-dazzle, the concept is a serious tech showcase for next-gen batteries and
propulsion, UX/HMI and BMW's' critical Neue Klasse architecture.
The technology below the smooth skin of BMW's
i Vision Dee concept car, unveiled at CES 2023,
marks a major step forward in the company's
electric-vehicle competitiveness. Models based
on the automaker's Neue Klasse EV architecture
will ditch today's rectangular prismatic batteries
for the type of large, cylindrical-form-factor cells
that Tesla is pioneering with its " 4680 " cells, so
named for their 46 mm x 80 mm dimensions. For
its sixth-generation EV batteries, BMW and its
battery partners - including China's CATL and
EVE Energy - will adopt even-larger cells of
" 4595 " and " 46120 " sizes.
At a pre-CES media backgrounder held in
Munich in December 2022, Martin Schuster,
BMW Group VP for high-voltage batteries, said
the new cells pack at least 10% more active
battery material relative to their metal cases
and are 20% more energy-dense.
For BMW's Neue Klasse platform, space and
weight are saved by using the battery pack as
a structural, crash-resistant chassis member:
the entire floorpan yawns open until the pack
fills the gap. That " pack-to-open-body " design
will allow BMW tailor battery sizes to a wide
range of vehicles and applications: Pack sizes
can range from 75 kWh to a beefy 150 kWh,
with motor output ranging from an estimated
268 hp (200 kW) to a dizzying 1341 hp (1000
kW). The design also saves more than 10 mm
(0.39 in.) in vehicle height, reducing costs and
lowering the center of gravity while improving
aerodynamics. BMW executives, including CTO
Frank Weber, said the goal is to squeeze more
6 February 2023
miles from every cell, not to cram ever-larger
batteries aboard.
" Going big on cell power and extreme range
is not the solution, because the size and weight
penalty is counterproductive, " Weber said.
" Instead, we must get the best out of every
watt-hour by further reducing rolling resistance,
improving aerodynamics and increasing
onboard energy efficiency. "
Favoring the cylindrical form factor
Compared with more-volatile prismatic cells,
whose myriad circuit connections make it harder
to protect against runaway heat and potential
fires, each heat-shielded cylindrical cell can
be individually monitored and isolated to avoid
thermal runaway, the engineers noted. The new
layout also eliminates a modular structure that
required removing the pack to access electronic
controls - currently the chief source of
BMW EV maintenance issues.
Next, an improved nickel-cobalt-manganese
(NCM) chemistry reduces by 50% the cathodes'
content of cobalt (pricey and often ethically
sketchy in its sourcing), with 20% less graphite
in the anode. Like other automakers, BMW will
continue to beef up silicon content in anodes to
boost efficiency and performance (BMW also
repeated a bold claim to have a 100% solid-state
battery in a BMW Group model by 2030).
Executives confirmed the Neue Klasse design
also will support lithium-iron phosphate (LFP)
cell chemistry for lower-end BMW Group models.
LFP, rapidly gaining industry popularity, is
Andrew Jeffers
Treasurer
David L. Schutt, Ph.D
Chief Executive Officer
Gregory L. Bradley, Esq.
Secretary
Judy Curran
Mary Lee Gambone
Michael Weinert
Joan Wills
SAE International Sections
SAE International Sections are local
units comprised of 100 or more SAE
International Members in a defined
technical or geographic area. The purpose
of local Sections is to meet the technical,
developmental, and personal needs of the
SAE Members in a given area. For more
information, please visit sae.org/sections
or contact SAE Member Relations Specialist
Abby Hartman at abby.hartman@sae.org.
SAE International
Collegiate Chapters
Collegiate Chapters are a way for SAE
International Student Members to get
together on their campus and develop
skills in a student-run and -elected
environment. Student Members are vital
to the continued success and future of
SAE. While your course work teaches
you the engineering knowledge you
need, participation in your SAE Collegiate
Chapter can develop or enhance other
important skills, including leadership,
time management, project management,
communications, organization, planning,
delegation, budgeting, and finance. For
more information, please visit students.
sae.org/chapters/collegiate/ or contact
SAE Member Relations Specialist Abby
Hartman at abby.hartman@sae.org.
AUTOMOTIVE ENGINEERING
BMW
http://www.sae.org/sections http://www.sae.org/chapters/collegiate/

Automotive Engineering - February 2023

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