Automotive Engineering - March 2023 - 28

Deep breathing
for EV batteries
Optimum venting is
a key to maximizing
EV battery pack
performance and
safety. An expert offers
five important design
considerations.
by Shane Campbell
Optimized battery venting is vital to ensuring
system integrity in edge cases such as when
the EV fords cool water deep enough to put
the warm battery pack into thermal shock and
cause a rapid vacuum event. Shown is a VW
pack undergoing water immersion testing at
the OEM's Chattanooga, Tenn., facility.
A
s EV batteries become more sophisticated, the need to protect
them from the elements has never been greater. Battery
pack engineers understand vehicle applications and by marrying
them with proper venting technology, they are helping
to advance EV performance and safety.
Five important design considerations to help maximize EV battery
pack performance:
1. Provide pressure equalization
Temperature and elevation changes can cause pressure variations
inside a pack enclosure. Vents allow air to flow in and out of the enclosure,
which helps equalize the pressure. Greater airflow allows
faster equalization and lower maximum pressure differentials. As
pressure builds in an operating system, the weakest point will be
found, so a properly designed vent takes the pressure off sensitive
components within a vehicle and helps maintain proper airflow.
The rate of pressure change also needs to be considered. Pressure
changes often are driven by temperature changes inside the battery
pack due to environmental conditions, charging and discharging. As
the rate of pressure change increases, more airflow is required.
To handle fluctuating pressure changes, the size and number of
vents, type of membrane, airflow properties and outside conditions
need to be considered at the onset of development. Implementing the
appropriate type and number of battery pack vents can help manage
the internal pack pressure at differential operating conditions.
2. Engineer for ingress protection
While airflow requirements are critical to managing pressure levels in
battery packs, ingress protection to keep out contaminants also is an
28 March 2023
important consideration. A key parameter to use during
the design and testing phases is the ingress protection
(IP) rating, which indicates the effectiveness of sealing
enclosures against foreign bodies and moisture.
Typical contaminants a battery vent must protect
against include water (spray and submersion), oil, dust,
and sand particles. Donaldson's dual-stage battery vents,
for example, utilize a unique body design and Tetratex
ePTFE membrane - a proprietary filtration media - to
provide exceptional battery pack protection.
As ingress protection is increased, emergency degassing
airflow may be decreased, so proper venting
solutions need to find the optimal balance between
ingress protection and degassing airflow.
3. Account for edge cases
EV battery packs and enclosures are created to handle
unexpected edge cases, which are events that occur at
extreme operating parameters. While edge cases occur
infrequently, it's important that a venting solution is optimized
to help reduce the risk of damage to the battery
pack and mitigate component failure or costly repair.
Examples of edge-case scenarios:
* DC fast charging - This charging process is significantly
faster than Level 2 (AC) charging stations and
generates extra heat and pressure on an EV battery.
* Hill climbs - The competitive sport of uphill racing
(i.e., Pike's Peak) causes a sudden change in altitude
and increases the pressure and temperature in a
vehicle battery.
AUTOMOTIVE ENGINEERING
LINDSAY BROOKE
Automotive Engineering - March 2023

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