Transient Voltage Threatens EV Charger Reliability

Key Takeaways

Transient voltage is a silent reliability threat. Short, high-energy voltage spikes—often invisible during normal operation—can degrade Electric Vehicle (EV) charger components, cause communication errors, and shorten equipment life.
Damage doesn’t always come from the grid. Many harmful surges can originate within a facility itself—from switching motors, HVAC systems, or other power electronics—not just from utility disturbances.
Layered surge protection is essential. Cascaded surge protection and robust grounding prevent costly downtime and extend the lifespan of both chargers and connected vehicles.

Introduction

As electric vehicle adoption accelerates, charging infrastructure is expanding rapidly to meet demand. But alongside the visible challenges of site design, capacity planning, and interoperability lies a less obvious but equally critical issue: transient voltage.

Transient voltage events—short, high-voltage spikes—pose a serious threat to EV charging systems. Left unaddressed, these disturbances can degrade, disrupt, or even destroy sensitive components in both chargers and connected vehicles.

Understanding transient Voltage

Transient voltages, more often called “surges,” are brief but intense deviations from normal voltage levels. These events originate from several sources:

External: Lightning strikes, grid switching, or faults in nearby utility equipment.
Internal: Switching operations from motors, HVAC systems, or even the chargers themselves, which contain high-frequency power electronics. According to ESFi, 60 to 80% of surges originate from equipment inside buildings/facilities.

Over time, these small but frequent surges degrade insulation, circuit boards, and other electronics within connected systems—everything from building automation controls and lighting to production equipment. Without proper voltage mitigation, the cumulative effect is premature equipment failure, unexplained downtime, and reduced efficiency.

How Power Surges Affect EV Chargers

Modern EV chargers contain AC/DC converters, communication circuits, and control boards that coordinate complex energy transfer between grid and vehicle. These circuits are finely tuned and easily disrupted by transient voltage events.

Impacts of transient voltage include:

Component stress and degradation: Repeated exposure erodes semiconductor junctions, insulation, and capacitors, reducing lifespan.

Interruption of charging sessions: Spikes can trigger system lockups, error codes, or unexpected shutdowns, frustrating users and affecting uptime and charging station throughput.
Permanent damage: A single surge has the capacity to damage control boards, rectifiers, or network communication modules—leading to costly repairs or replacements.

Impact On Connected Vehicles

Transient voltage may propagate through the charger to connected vehicles. While onboard chargers have protective circuitry, they are not immune.

Potential consequences include:

Battery management system (BMS) disruption: Voltage spikes can cause communication errors or charging faults.
Long-term wear: Repeated exposure accelerates component aging and may impact battery or electronic reliability over time. In fleet or commercial applications, where vehicles connect and disconnect multiple times per day, these risks multiply.

For guidance on battery life best practices, review "Best Practices: Extending the Life of Lithium-Ion Batteries"

Read Now

Study: Power Quality Risks in EV Chargers

A 2020 field investigation examined EV charger installations and the effects of source-side power quality (PQ) events on charger reliability.⁶

The study found that EV chargers experienced measurable damage and malfunction due to transient voltages originating not only from the utility but also from on-site electrical disturbances.

The study emphasized the need for site-level power quality monitoring and layered surge protection. These findings reinforce that transient voltage is not an abstract engineering concept—it’s a measurable, field-documented cause of charger malfunction and early component failure.

Mitigating Transient Voltage Damage

Protecting EV infrastructure requires a layered approach that addresses both external and internal transient sources:

Install surge protection devices (SPDs): High-performance SPDs should be applied in a cascade method across the facility—from main distribution panels to branch circuits and at the equipment level—to ensure surges are safely mitigated to equipment immunity levels.
Harmonic Mitigation & Filtering: Use passive harmonic filters to reduce distortion produced during charging. Also, verify system resonances to avoid unintended amplification of transient voltage effects.

Implement robust grounding and bonding: Ensure all metallic structures and electrical systems share a common ground potential. Poor bonding allows transient voltage to flow unpredictably through control circuits.

The Cost of Inaction

Even minor transient overvoltage events can add up over time, gradually shortening component life, increasing maintenance costs, and reducing charger availability. In mission-critical settings, like fleet depots or public charging corridors, any downtime directly leads to lost revenue and frustrated customers.

Investing in voltage protection isn’t just about safeguarding hardware; it’s about ensuring reliability, safety, and maintaining customer trust in the EV ecosystem.

Conclusion

As the world transitions toward electrified transportation, power quality must be treated as a foundational design element—not an afterthought. Transient voltage protection safeguards the substantial investment behind EV charging networks, preserving uptime, performance, and the long-term health of connected vehicles.

Resources

Electric Power Research Institute. Best Practices for Electric Vehicle Supply Equipment (EVSE) Installation. EPRI, 2022.
IEEE Power & Energy Society. “Considerations for Power Quality in Electric Vehicle Charging Systems.” IEEE Transactions on Power Delivery, vol. 38, no. 2, 2023, pp. 1104–1116.
National Fire Protection Association. NFPA 70: National Electrical Code (NEC), 2023 Edition. NFPA, 2023.
Open Charge Alliance. OCPP 2.0.1 Specification. 2020.
U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy. Electric Vehicle Charging Infrastructure Trends from the Alternative Fueling Station Locator: Fourth Quarter 2023. DOE, 2024.
“Electric Vehicle Charger Case Study.” PowerQuality.blog, 2020, https://powerquality.blog/wp-content/uploads/2020/11/electric-vehicle-charger-case-study-1.pdf.