Top Engineering Concern: Why Do Contactors Fail in Low-Temperature Environments?

As electrification accelerates across EVs, charging stations, and energy storage systems, engineers are facing a growing challenge: DC contactors failing under low-temperature conditions. From northern Europe to North America and northern China, harsh winter climates are revealing weaknesses in many electromechanical systems — and contactors are among the most affected.

At the same time, global industry reports and field data show increasing attention on cold-weather reliability:

Several EV charging networks in Canada have reported reduced charging availability during winter due to component freezing issues.

Nordic energy storage projects increasingly emphasize the need for ultra-low-temperature-rated switching devices in procurement specifications.

U.S. Department of Energy (DOE) winter testing has identified contact interruption failures as a major reliability risk for DC systems operating below –20°C.

So why are low temperatures such a critical threat to contactors? And what design considerations matter most for modern electrification systems?

1. Coil Performance Drops in Extreme Cold

A DC contactor relies on its coil to generate a magnetic field strong enough to pull in and hold the contacts. At very low temperatures:

• Coil resistance decreases, causing higher inrush current

• Magnetic force may weaken due to material characteristics

• Pull-in voltage increases, meaning the contactor may fail to close

Result: Contact bounce, delayed closing, or complete failure to operate.

2. Grease and Mechanical Components Become Stiff

Traditional lubricants thicken in cold environments, making mechanical motion sluggish:

• Armature movement slows down

• Return springs lose elasticity

• Contact travel becomes unstable

This leads to slow response, partial closure, or increased wear.

Field data from cold-region installations show that a significant portion of winter failures in DC switching equipment are linked to stiffened mechanical components caused by sub-zero temperatures.

3. Contact Resistance Increases at Low Temperatures

Metal behaves differently in cold conditions:

• Conductive surfaces contract

• Micro-surface roughness increases

• Actual contact area decreases

This can cause:

• Higher heat generation during load switching

• Localized hotspots

• Accelerated contact erosion

Under high-voltage DC operation, even small resistance increases can significantly raise failure risks.

4. Material Brittleness Leads to Structural Damage

At temperatures below –40°C, certain metals and plastics become brittle:

• Coil insulation may crack

• Ceramic or plastic housings may fracture

• Terminal welding points may weaken

Cold-climate energy storage installations have reported cases where low-temperature brittleness caused contactor structural failures, triggering emergency system shutdowns.

5. Frost and Condensation Create Insulation Problems

Repeated freeze–thaw cycles lead to moisture accumulation:

• Condensation forms during daytime warming

• Freezes at night

• Repeats continuously

Effects include:

• Insulation degradation

• Surface leakage currents

• Corrosion on contact surfaces

This is especially dangerous in energy storage systems and EV chargers, where high-voltage DC insulation integrity is critical.

How Engineers Are Responding

With the expansion of electrification into cold climates, engineers now prioritize:

✔ Low-temperature-rated coils
Designed for reliable operation at –40°C or even –55°C.

✔ Special low-temperature lubricants
Ensuring stable mechanical movement without stiffness.

✔ Silver-based or tungsten-based contact materials
Reducing resistance growth and arc erosion.

✔ Enhanced sealing and anti-condensation designs
Preventing moisture ingress into contact chambers.

✔ Mechanical structures optimized for low-temperature elasticity
Reducing brittleness under extreme cold.

Industry R&D trends show that low-temperature reliability has become a key purchasing criterion for DC contactors used in critical power systems.

Conclusion: Choosing the Right Contactor Prevents Winter Failures

As EV charging systems expand into colder regions and outdoor energy storage installations increase, low-temperature performance is no longer optional — it is essential.

A high-quality DC contactor designed for sub-zero environments can:

• Prevent system shutdowns during peak winter demand

• Extend overall system lifespan

• Reduce maintenance and replacement costs

• Ensure safe, stable operation of charging and storage systems

For engineers and project managers, selecting a low-temperature-rated contactor means avoiding costly failures and protecting the entire system as climate conditions become more demanding.