NDT FOR ELECTRIFIED VEHICLES: BEYOND
BATTERY CELL INSPECTION
BY MEGAN MCGOVERN, ERIK HUEMILLER, DMITRIY BRUDER,
SEAN WAGNER, ROBIN JAMES, AND RASHMI PRASAD
While battery cells dominate the conversation around nondestructive
testing (NDT) for electric vehicles, focusing too narrowly on them
risks overlooking other critical components. Electric motors, power
electronics, battery modules, and related systems also demand rigorous
inspection to ensure vehicle safety and performance. Recognizing
these often-overlooked NDT applications reveals their essential role in
supporting the future of electrified mobility.
Introduction
Publications on nondestructive testing
(NDT) of electric vehicle (EV) compo-
nents are, understandably, heavily dom-
inated by battery cell inspection applica-
tions [1–4]. This dominance is justified,
since battery cells are the single most
crucial and distinguishing feature of
vehicle electrification—e.g., EVs, hybrids,
plug-in hybrids, and extended-range
electric vehicles (EREVs). Cells must
operate as intended to ensure maximum
range, safety, and performance.
However, the heavy emphasis on battery
cells in the literature may lead those
unfamiliar with EVs to overlook NDT for
other essential components. Although
automotive engineers recognize the
importance of non-cell components,
the authors’ purpose here is to famil-
iarize the reader with NDT inspection
for several of the non-cell components
required for electrified vehicle opera-
tion. While these discussion points apply
to all electrified vehicles (e.g., hybrids,
plug-in hybrids, EREVs), only “EVs” will
be referred to throughout this article for
simplicity. Figure 1 presents a simpli-
fied schematic of these various vehicle
architectures.
Non-Cell NDT for Electrified Vehicles
The importance of NDT in EV design
cannot be overstated. NDT is crucial
for ensuring safety and performance,
serving as a safeguard against issues
such as desoldering or delamination
of parts that can lead to catastrophic
failures. It also verifies that the vehicle
and its components comply with spec-
ifications. NDT for EVs is used at every
stage of the vehicle’s life: at the com-
ponent manufacturing level, during
vehicle assembly, throughout in-service
operation, and even to support root-
cause investigations through post-failure
FEATURE
|
NDTTUTORIAL
Hybrid electric vehicle &
plug-in hybrid electric vehicle
*Only parallel configuration shown
Extended-range electric vehicleBattery electric vehicleInternal combustion engine
ICE BEV HEV EREV
PHEV
Figure 1. Simplified schematic showing high-level differences between architectures: (a) internal combustion engine (ICE) (b) battery electric
vehicle (BEV) (c) hybrid and plug-in electric vehicle (HEV/PHEV) (d) extended-range electric vehicle (EREV). Note: These schematics are for
illustration purposes only and are not meant to accurately depict vehicle architectures. (Images of components, including the battery and electric
motor, appear from [5–7] with permission.)
26
M AT E R I A L S E V A L U AT I O N • J A N U A R Y 2 0 2 6

teardowns for any warranty issues. The
primary distinction between electri-
fied vehicles and internal combustion
engine (ICE) vehicles lies in their pro-
pulsion systems. EVs use an electric
motor powered by a battery pack, with
lithium-ion cells currently the predom-
inant commercial cell type, whereas
ICE vehicles rely on hydrocarbon-based
fuels. Consequently, greater emphasis
is placed on the integrity of certain EV
component groups, including electrical
and mechanical joints, thermal interface
materials, hermetic sealing, and electri-
cal insulation, since they must withstand
a different set of loads than ICE vehicles.
The following sections take a closer
look at these components and share
EV-specific examples.
Battery cells have been extensively
documented in existing literature [1–4]
therefore, we will instead provide
examples that focus on other EV com-
ponents, such as electric motors, power
electronics, and modules. It is important
to clarify some nomenclature: “modules”
refer to subassemblies comprised of
battery cells. These modules are then
assembled to form a battery pack (see
Figure 2). Although not all battery packs
are modular, many NDT applications
occur at the module level, so modules
will serve as a frequent example
throughout this article.
Choosing the Appropriate NDT
Method
When inspection is feasible and con-
tributes meaningfully to safety, it takes
priority over all other considerations. In
non-safety-related scenarios, however,
selecting the most suitable NDT method
for a given component depends on
several factors, including inspection
accessibility, testing time, method
durability, and cost. Accessibility chal-
lenges vary depending on whether the
inspection occurs during manufacturing
(when components are generally more
exposed) or after final vehicle assembly
(when access is often restricted).
In high-volume, in-line manufactur-
ing environments, cycle time and cost
are typically the most influential factors
in NDT method selection. Additionally,
the durability of the NDT system
becomes critical, as it must withstand
repeated use under tight cycle time
constraints with minimal maintenance
downtime. In fact, system durability and
cycle time requirements are among the
most demanding challenges for NDT
techniques in the automotive sector.
Compared to other industries, automo-
tive production demands NDT technol-
ogies that operate faster and inspect a
significantly larger number of parts. Any
viable NDT method must be capable of
meeting these rigorous demands.
A clear example of these constraints
is the inspection of battery module
welds. These welds require 100% in-line
inspection, as even a single defect can
compromise module performance. This
requirement imposes strict demands on
inspection speed, reliability, and system
durability.
Mechanical and Electrical
Connections
Bonds and joints in EVs serve as essen-
tial mechanical, electrical, and thermal
connections (thermal connections will
be discussed in this section). Mechanical
joints are designed to withstand both
dynamic and static loads encountered
by the vehicle and its components.
Electrical joints must enable current
flow without excessive resistance or heat
generation, and many connections fulfill
both roles. Given their critical function
in vehicle performance, it is imperative
to nondestructively assess these con-
nections to verify that they meet speci-
fications. While both connection types
exist in ICE vehicles, the electrical joints
found in EVs must handle higher elec-
trical loads while maintaining structural
integrity. For example, the battery cell
tab-to-busbar welds in modules connect
battery cells in parallel or series via a
busbar and must also withstand vehicle
operational loads.
PERMANENT CONNECTIONS
Traditional NDT methods such as ultra-
sound and visual inspection are reliable
for inspecting structural body welds
and joints. These joints can take several
forms, including resistance spot welds
or adhesive-bonded joints. Inspection
of these joints is critical, since the struc-
tural joints on the car body are crucial
for passenger safety—both during opera-
tion and in the event of an accident—for
EVs and ICE vehicles alike. Other NDT
methods, such as thermography and
direct radiography, should be considered
as areas of research where conventional
approaches are insufficient.
Machine vision [9], thermography
[10], and electrical performance tests
(such as four-point probe resistance
measurement) are often suitable for
electrical joints, including the afore-
mentioned module tab-to-busbar welds.
Electrical joints face the additional
constraint of requiring noncontact
inspection solutions since they are ener-
gized. Thermography, in particular, is
a powerful noncontact inspection tool
[11, 12]. However, it encounters difficul-
ties with parts that have low emissivity
(i.e., high reflectivity), which is often the
case for metal electrical joints. While
applying a surface coating, such as
paint, to enhance emissivity is common
practice, this approach is often not
feasible for electrical joints. Alternative
reflection-mitigating strategies may then
be employed.
Figure 2. Example of a modular battery pack where (a) cells are assembled into a module, and
(b) modules are assembled into a pack. (Images used from [8] with permission.)
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