Automotive Engineering - March 2023 - 29

BATTERY VENTING FEATURE
Added dual-stage battery vents reduces battery pack pressure buildup during
temperature changes. Calculations shown assume a free air volume of 20 liters
and a temperature change of 45C over 12 minutes.
Exploded view of a dual-stage burst vent.
* Water fording - Driving off-road through a creek, for
example, can put a warm battery pack in thermal
shock; the cool water can cause a rapid vacuum event.
* Air transportation - A vehicle being transported
within a cargo aircraft will be impacted by pressure
changes from the altitude variation.
* Rock impact - Rocks or other debris hitting the
undercarriage of a vehicle can cause a pressure
spike inside the battery pack.
Our testing process includes a comprehensive design
failure mode and effect analysis. This analysis
looks at the severity and frequency of possible edge
cases and tracks them in a validation plan. We work
with customers to understand what extreme conditions
their vehicles may experience and what requirements
are needed to retain driving performance during
a sudden edge case scenario.
4. Mitigate emergency degassing events
As with edge cases, optimum battery pack vent design
helps manage emergency degassing events, such
as a thermal runaway. Such events happen when pressure
rises to a concerning level and gas needs to be
immediately released from the pack.
Dual-stage venting solutions are designed to help
manage escalated situations. Stage one equalizes
pressure while preventing the ingress of water and
contaminants. Stage two venting fully opens in response
to rapid pressure and heat buildup to allow
expanding gases to escape and reduce further damage
to remaining cells. In most situations, a single vent
AUTOMOTIVE ENGINEERING
assembly can accomplish both functions. This mechanism helps prevent
further damage to battery cells or a pack enclosure.
5. Perform a full temperature-range validation
Our engineering and product teams design battery pack vents to
operate in a variety of operating temperatures. We frequently perform
tests in a full range of extreme temperatures to see how our
vents handle burst pressure, emergency degassing, pressure cycle,
thermal cycle, thermal soak, thermal shock and vibration.
Venting is a critical component of EV battery thermal management.
As temperatures rise or fall, a breathable vent provides pressure
equalization to protect battery housing seals. We work directly
with OEMs to ensure vents are tested across the full range of temperatures
experienced in an EV battery pack.
The demand for innovative EV batteries that provide more power
and longer range will continue, with advanced battery
pack vent designs playing a major role. They must protect
against any situation that arises while on the road.
Shane Campbell, a graduate chemical engineer and productdevelopment
veteran, is a product manager in Donaldson's
Integrated Venting Solutions business unit.
March 2023 29
A closeup of Donaldson's Tetratex media. This expanded ePTFE membrane has
a unique microstructure that is naturally hydrophobic and offers protection from
temperature and thermal fluctuations, moisture and other harmful contaminants.
ALL IMAGES: DONALDSON CORP.
Automotive Engineering - March 2023

Table of Contents for the Digital Edition of Automotive Engineering - March 2023
