The Complete Guide to Dielectric Coating for EV Battery Assemblies: Edge Issues
Epoxy powder coatings have been successfully used to insulate copper buss bars used in
electrical switchgear for decades. The development of high-voltage battery systems used in
modern BEV vehicles has increased demand for insulation coatings to prevent arcing between
metal components within the battery enclosure. However, repurposing these proven insulation
coatings from the simple geometry of copper buss bars to thin-gauge, complex aluminium
components presents a number of challenges for successful implementation.
This series of articles discusses some of the key challenges that need to be overcome to deliver
a satisfactory solution.
Challenge 1 – Cut edges issues in dielectric coating process.
Dielectric coatings tend to thin at edges, particularly around sheared metal corners and smallradius features, where the geometry can resist even coverage. Even a minor reduction in coating thickness at an edge can lower insulation resistance below acceptable thresholds, leading to
partial discharge, electrical arcing, or outright machine failure.
Microscopic view of a sheared edge.
What are the key challenges in getting electrical insulation properties around cut
edges?
The primary purpose of a dielectric coating is to electrically insulate components to a specified
voltage. The dielectric strength of the coating, measured in kV/mm, allows a simple calculation
of the minimum coating thickness required to provide insulation resistance.
On flat surfaces, dielectric coating is easily accomplished, but cut edges provide a challenge.
Due to a surface tension effect, coatings have a tendency to pull away from sharp edges,
reducing the thickness and, hence, the isolation resistance in the case of dielectric coatings
Microscopic view of how the coating pulls away around the edges.
Both the shape and edge radius contribute to the reduction in paint thickness.
The edge geometry is determined by the forming process so shearing, laser cutting, stamping,
sawing will develop a different profile.
Different edges formed based on forming techniques.
At Powdertech, they understand this and advise involving experts from the prototype stage and
not just post production to ensure that the coating is right the first time.
They have studied different coating systems and their interaction with different edge geometries
to provide a working solution for a variety of applications.
Tackle edge burrs in dielectric coating process with Powdertech.
- By altering the edge geometry, pre-treatment compatibility, masking strategies and
thickness targets they can tailor the properties to the required specification requirements.
- Tailoring your powder coating process, including coating thickness, number of coats and
other elements, to ensure you reach the required insulation properties as per your spec.
-Powdertech advise on handling the parts right, this is a crucial aspect to avoid edge defects
as thin aluminium components are more prone to edge damage.
Dielectric Coating Testing at Powdertech
Testing is crucial and Powdertech’s team brings decades of technical experience to support all
your needs from start to finish.
They conduct HI-Pot testing, Holiday testing and cross-sectional microscopy to gauge if dielectric
coating has met specifications. This allows them to verify coating integrity before final
deployment.
At Powdertech, they have an in-house testing facility to ensure the accuracy of the dielectric
coating in EV battery systems.
Dielectric coating represented through edge A has the higher passing rate when tested via Holiday testing. The test and dielectric coating were conducted for one of their biggest automotive clients.
Powdertech’s lab-tested methods, dielectric coating experience, and collaboration at each
stage means your dielectric coating performs where it matters most, even at the edges.