Automotive Engineering - March 2023 - 21

BATTERY PACK TRENDS FEATURE
BATTLE
BOX
FOR THE
EV battery enclosures are
a hotbed of subsystem
design, materials
innovation and vehicle
integration.
by Lindsay Brooke
Inside Novelis' stateof-art
Gen-II battery
enclosure, from the
top: Aluminum top
cover; advanced
cell-to-pack battery
system (green); s701
and s650 roll-formed
AL profiles; simple
modular extruded
frame enclosure;
structurally integrated
cooling plate (blue),
fire resistant AL
bottom plate.
W
hether you call them packs, boxes or
trays, the structures that envelop and
protect EV battery cells and their supporting
electrical and thermal-management
hardware are among the industry's top subsystem
priorities. Optimizing the battery pack involves a
host of manufacturing and material choices, mass and
package tradeoffs, safety provisions and structural
design/engineering challenges, OEM and supplier experts
told SAE Media.
" Do you want the battery pack bolted into the vehicle
or integrated into the body structure? " asked Darren
Womack, senior department manager, body and structures,
at Magna's global R&D group. Hot stamping, cold
stamping, roll-forming, hydroforming, casting and steel,
aluminum, composites and thermoplastics - are all
raising " lively discussions " in pack development, he noted
at a recent meeting of analysts.
OEMs clearly want to eliminate redundant structure
to optimize package space and reduce mass and complexity,
Womack noted. Integrating the EV battery into
its surrounding platform involves various configurations.
Cell-to-pack design, currently in production at
BYD, does away with the intermediate module stage,
putting the cells directly into the pack. Cell-to-chassis
technology integrates the battery cell with the vehicle
chassis, electric drive and thermal management. All
battery components are housed in the vehicle bodyin-white,
eliminating the separate pack.
In such setups, under investigation by Tesla and others,
the chassis pan and vehicle side structure double
AUTOMOTIVE ENGINEERING
as the battery's bottom plate and sides. In this marriage, impact integrity,
accurate pack assembly, and robust sealing are paramount.
" Each OEM is going to want a 'playbook'- a menu of options
based on their criteria including cell form factor, battery size, and
vehicle, " explained Mario Greco, director of strategy and marketing,
Global Automotive, at aluminum specialist Novelis. " No single solution
for battery enclosures is going to fit everybody. "
For example, a high-volume solution may be a stamped, singlepiece
enclosure. It might include an integrated cooling structure because
the vehicle architecture lends itself to a cell-to-chassis design
versus a cell-to-pack, he said. " I think we'll see a convergence between
the 'skateboard' and next-generation unibody architectures, "
Greco noted, " because the OEM incumbents that are stepping into
EVs have all-new unibody architectures that are designed to serve
them for quite a while. "
Wide-open field for design
Despite the significant mass burden of liquid-cooled lithium battery
packs, EV mass-reduction improvements are still possible, according
to Gregor Klement, global chief engineer, Battery Trays, at Magna.
" Looking into the future, we see more and more integration of the
battery into the vehicle body, " he said, with light metals and composites
both playing a role. " Magna R&D is working on cell-to-chassis
solutions, and we see customers looking in a similar direction. By
eliminating redundant structural parts, we see opportunity for good
improvement in weight and cost. " But he reckons battery weight likely
will never be completely offset.
With vehicle electrification still in its nascent phase, much EV subsystems
development is on the critical path, noted Jeremy Loveday,
program engineering manager on Cadillac's superluxury 2024 Celestiq.
March 2023 21
NOVELIS
Automotive Engineering - March 2023

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