The Complete Guide on 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 have 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 present 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. 

Microscopic view of a sheared edge. 

Challenge 1 – Cut edge issues in dielectric coating process. 

Dielectric coatings tend to thin at edges, particularly around sheared metal corners and small-radius 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.  

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 the required insulation resistance. 

Microscopic view of how the coating pulls away around the edges which leads to a lower ERR.

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. 

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. 

At Powdertech, we 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. 

We have studied different coating systems and their interaction with different edge geometries to provide a working solution for a variety of applications. 

How to tackle with edge issues in dielectric coating process?

- By altering the edge geometry, pre-treatment compatibility, masking strategies and thickness targets, we 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. 

-We 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 Surface Science’s team brings decades of technical experience to support all your needs from start to finish. 

We conduct HI-Pot testing, Holiday testing and cross-sectional microscopy to gauge if dielectric coating has met specifications. This allows us to verify coating integrity before final deployment. At Powdertech, we have a in-house testing facility to ensure the accuracy of the dielectric coating in EV battery systems.  

Our lab-tested methods, dielectric coating experience, and collaboration at each stage means your dielectric coating performs where it matters most, even at the edges.  

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 our biggest automotive clients.