Automotive Engineering - March 2022 - 16

Proving technology in a 752-mile run
To demonstrate their battery-tech prowess and increase the
company's visibility, ONE engineers in December 2021 removed
the stock 104-kWh battery pack from a Tesla Model
S Long Range Plus sedan and replaced it with their own
207-kWh prototype pack, which fit nicely within the Model
S's confines. They then set out from ONE's suburban Detroit
headquarters into the Michigan heartland. After fourteen
battery-draining hours of flogging the Tesla at an average
speed of 55 mph (88 km/h), the team had covered 752.2
miles on a single charge.
In stock form, the longest-range Model S was rated by the
U.S. EPA at 402 e-mpg. In 2020, Car and Driver magazine
testers traveled 320 miles (515 km) at a sustained 75 mph (120
km/h) in the same Tesla-S model, a record distance for any
vehicle tested by the publication at the time. The standard
Model S has a drag coefficient of 0.24, according to Tesla.
Following the real-roads exercise, the team put the
ONE-fortified Tesla on a chassis dynamometer at a sustained
55 mph, stretching its legs for 882 miles on a single
charge. The prototype battery exercises (which used special
cobalt-nickel chemistry) showed encouraging potential for
the future of lithium batteries and EV range.
LB
A prototype Aries LFP pack prior to delivery for customer testing.
The structural cell-to-pack concept embraced by ONE and other
battery suppliers including BYD (https://www.sae.org/news/2021/10/
byds-blade-runner) does away with modules, integrating the cells
themselves into the pack architecture for increased package and mass
efficiency. Ijaz explained his team's engineering rationale, noting that
cell-to-pack requires three conditions for it to be a rational solution.
" First, the chemistry has to be right, " he said, calling LFP " the birth
center " of cell-to-pack. " A chemistry that tends to self-oxidize is not
feasible; if a failure occurs and the chemistry self-oxidizes, it will rip
through the pack because the cells are so intimate, " he said. " You
can't stop the spread of a thermal runaway. "
Secondly, cell form factor is important. Of the four primary types
of lithium cell used in EVs, the pouch types are non-starters.
" For cell-to-pack to work, you need to create a load path that's
load carrying; a pouch cell needs to be surrounded by a module, " he
explained. Metal cans and the " blade " type cell (used by BYD) function
as stressed members and so are acceptable. And cell-to-pack
structures present a challenge in terms of serviceability; Ijaz argues
that serviceability has to be given up.
16 March 2022
The Tesla S fortified with a ONE high-energy prototype battery,
being prepped for its 752-mile test run.
" An EV battery is large and expensive, representing
about 40 percent of the vehicle's cost, " he said. " To
make the battery serviceable is not logical.
" Years ago, we believed that the OEM must be able
to service the battery pack. Now, with a decade of EV
experience behind us, the industry is learning that battery
cells aren't failing.
" Electronics fail, " he conceded, " but typically not the
cells. You and the customer have to agree that you're
not going to replace cells, which then becomes a warranty
and validation topic. "
AUTOMOTIVE ENGINEERING
FROM LEFT: LINDSAY BROOKE; ONE
https://www.sae.org/news/2021/10/byds-blade-runner
Automotive Engineering - March 2022

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