Some of the most important dimensions in an electric vehicle (EV) are the ones no one sees. A deviation of only 100 microns in battery cell spacing can affect cooling pathways and raise the risk of hotspots or electrical faults. At that scale, feeler gauges and mechanical shims can’t deliver the accuracy EV systems require.
Below, Scott Arnold of Capacitec explains how capacitive sensors measure these gaps and why that data matters for EV safety and reliability. His answers are adapted from this article.
Why do gaps matter so much in EV design?
Electric vehicle (EV) engineering is defined as much by what cannot be seen as by what can. The “gaps” or unseen spaces between battery cells, slot die coating of electrode layers, cooling plates, electric motor housings, and composite joints have a significant influence on performance, safety, and durability.
Non-contact capacitive gap sensors are used to measure and control coating thickness during EV battery manufacturing. (Image: Capacitec).
Managing these dimensions with high accuracy has become critical to achieving the reliability and efficiency demanded of today’s EVs. The good news is that advances in sensor technology now make it possible to measure and control these gaps with the kind of precision and repeatability modern EV design demands.
How much can a small deviation affect an EV battery?
In EV manufacturing, gap measurement is an essential step in safety and function. For example, a deviation of only 100 microns in battery cell spacing can affect cooling pathways and insulation integrity, raising the risk of hotspots or electrical faults.
Thermal management systems also rely on carefully controlled gaps in cooling plates and laminations to regulate fluid flow and maintain uniform heat transfer. Even slight irregularities can result in uneven cooling and lower overall efficiency.
How do gap errors affect electric motors and drive units?
Electric motors and drive units are equally sensitive. Misaligned stator-to-housing air gaps introduce vibration, reduce electromagnetic efficiency, and accelerate wear on bearings and windings. What begins as a minor deviation in assembly can lower battery capacity, lead to inconsistent torque delivery, and cause premature component failure.
Errors in gap measurement are more than simple deviations from design specifications. They change how systems behave under load, heat, and vibration, and those changes can compound over time. The result is a shortened service life and a higher risk of failures in the field.
What are the limits of traditional gap measurement methods?
Historically, many industries relied on feeler gauges or mechanical shims to measure gaps. While simple, these methods lack the precision and repeatability required for EV systems. Mechanical tools can introduce operator error, wear over time, or even damage delicate composite and coated surfaces.
More significantly, they cannot capture digital data needed for statistical process control or long-term traceability. That’s where sensors are making a difference, ensuring better accuracy and providing the data EV engineers require.
How do capacitive non-contact sensors work?
Capacitive non-contact sensors address traditional limitations by measuring distance through the interaction of an electric field with conductive surfaces.
Unlike mechanical gauges, they do not rely on physical contact, which eliminates wear and avoids damage to delicate or coated materials. This makes them particularly effective for measuring mixed materials, such as composite-to-metal or composite-to-composite joints, which are commonly found in lightweight EV structures. Non-conductive surfaces routinely use capacitive spring contact sensors.
How do capacitive sensors compare with optical measurement methods?
Unlike optical systems, such as laser or vision-based measurement, these sensors are unaffected by reflectivity or geometry. They can achieve sub-micron resolution, providing consistent, repeatable results across operators.
They’re also designed to maintain accuracy in harsh manufacturing environments, where vibration and temperature variation can compromise measurements. This consistency is valuable in EV applications where aluminum housings, copper busbars, and carbon-fiber reinforced polymers are combined in tight assemblies.
How does sensor data fit into quality control?
These sensors integrate digital datalogging and wireless transfer, letting engineers track trends, validate process stability, and feed measurements directly into automated quality control systems, effectively closing the loop between design tolerances and production reality while enabling integration into closed-loop manufacturing.
What does this mean for EV manufacturers?
The integration of high-voltage systems, dense battery packs, and lightweight structural materials leaves little tolerance for error in EV design.
Capacitive sensing technologies allow manufacturers to confirm that battery assemblies maintain consistent spacing, thermal systems function as designed, and electric motor housings align with exacting precision.
In practice, this means that engineers can verify tolerances at scale, track variations across different manufacturing sites, and ensure compliance with the quality standards expected of automotive-grade components and assemblies. The result is a higher degree of confidence in safety and performance, which is essential for the safety and quality standards of EV manufacturing.
Filed Under: Featured Contributions, Q&As