Thermal sensors are temperature-sensing components used to measure and monitor heat in EV charging equipment and related electrical infrastructure. They provide real-time temperature data that helps protect components, prevent overheating, and maintain reliable charging performance through controls like temperature derating and fault shutdown.
Thermal sensors can be built into the charger, installed in connectors/cables, or added to distribution equipment such as sub-distribution boards (SDBs) and cabinets.
Why Thermal Sensors Matter in EV Charging
Temperature is one of the most important predictors of reliability and safety in charging systems. Thermal sensors help:
– Detect overheating early and prevent damage to electronics and wiring
– Trigger safe derating or shutdown before a fault escalates
– Reduce risk of connector overheating and contact degradation
– Improve uptime by enabling preventative maintenance based on trends
– Distinguish thermal limitations from load management power limits in performance monitoring
– Support safety monitoring in adjacent systems like stationary battery storage
For high-utilization public sites and fleet depots, thermal sensing is a key tool for reducing failures and unplanned downtime.
Where Thermal Sensors Are Commonly Used
Thermal sensors are typically placed in heat-sensitive or high-risk points, such as:
– Power electronics areas (power supplies, PFC stages, relays/contactors)
– Enclosure hotspots (near heat sinks, airflow bottlenecks)
– Socket and connector interfaces (contact temperature rise)
– Cable terminations and high-current junctions
– Distribution boards and feeder pillars (hot terminals, overloaded breakers)
– Battery storage enclosures and racks (module and ambient monitoring)
Sensor placement is as important as sensor selection because many failures start as localized hotspots.
What Thermal Sensors Enable
Thermal sensing supports both safety and operations:
– Temperature derating logic (step-down current to control heating)
– Fan control and cooling optimization (variable-speed fans)
– Fault detection (overtemperature trips, abnormal gradients)
– Trend analytics (slowly rising operating temperatures indicating wear)
– Alarm workflows and service prioritization via telemetry
When integrated with telemetry streaming, thermal data can power real-time alerts and predictive maintenance.
Common Thermal Sensor Types
Thermal sensing can be implemented using different technologies depending on accuracy, cost, and installation constraints:
– Thermistors (NTC/PTC) for compact, low-cost internal sensing
– RTDs (e.g., PT100/PT1000) for higher accuracy and stability
– Semiconductor temperature sensors (IC-based sensors) in control electronics
– Infrared sensors (less common in chargers, more for monitoring or inspection)
– Thermal switches (threshold-based cutoffs rather than continuous measurement)
Many systems use a mix: continuous sensors for control + threshold switches for safety backup.
Design and Integration Considerations
– Calibration and tolerance affect how early derating starts and how stable control is
– Sensor placement must reflect the true hotspot, not just ambient enclosure temperature
– Wiring and connectors for sensors must be robust to vibration, moisture, and service handling
– Thermal response time matters: slow sensors may react too late in fast overheating events
– Firmware should apply safe defaults if a sensor fails (fail-safe behavior)
– Data should be time-synchronized to correlate temperature with load and faults
Common Pitfalls
– Measuring only enclosure air temperature and missing connector/junction hotspots
– Poor sensor bonding to the monitored surface, creating inaccurate readings
– Over-sensitive thresholds that cause unnecessary derating and complaints
– Lack of monitoring/alerting, so thermal alarms don’t translate into action
– Not distinguishing thermal derating from grid limits or load balancing effects in reports
Related Glossary Terms
Thermal Management
Temperature Derating
Power Derating
Telemetry Streaming
Charger Uptime
Preventative Maintenance
Load Management
Stationary Battery Storage