THERMAL MANAGEMENT
1
“If a manufacturer uses simple
battery management systems
the battery can overheat or be
charged at too cold a temperature”
Professor Dr Andreas Hintennach, senior manager, battery research, Daimler AG
despite the number of crashes doubling as the
parc increased. Gasoline and fl ex-fuel vehicles
caught fi re in 3.4-3.5% of incidents respectively.
The materials used aren’t necessarily more
volatile. NHTSA research into battery fi res
showed that liquid diethyl and dimethyl
carbonate electrolytes used in today’s lithiumion
batteries have a similar fl ashpoint to fossil
fuels, dispersing as heavier-than-air vapors and
localizing fi res beneath the vehicle. The Agency
said fl ame-retardant alternatives, such as
fl uorinated and organophosphorus additives
could further reduce the risks.
its cars in 2018, 15% of which were
due to external factors such as
arson or nearby objects burning.
The US average is one fi re per 30.5
million km (19 million miles).
Paul Shearing, professor of
chemical engineering at
University College London
and Royal Academy of
Engineering chair for
emerging battery
technology, says it refl ects
well on the industry. “Some
manufacturing defects can
be latent for quite a long time,
then mature into something
more substantial, but it’s
important to emphasize that these
are very rare. Failure rate for all lithium-ion
batteries is somewhere between one in 10
million and one in 40 million cells. Not all fail
spectacularly – some fail in a more passive way
– but the failure rate is impressively low.”
In-life abuse is harder to avoid, particularly
short circuits caused by impact damage, but
protective structures used by car makers
appear to be eff ective. The National Highway
Tra c Safety Administration (NHTSA)’s most
recent data shows electric and hybrid cars only
caught fi re in 1.6% of fatal accidents in 2017.
That’s proportionally unchanged since 2013,
52 // January 2020 // www.electrichybridvehicletechnology.com
1. Envision-AESC has built
over 480,000 batteries
for Nissan’s EVs, with
reports of no critical
incidents globally
2. The Porsche Taycan
employs an 800V
architecture to enable
it to charge at rates of
up to 350kW without
the risk of overheating
2
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