DC Fast Charging: The Need for Speed and Precision
DC charging stations bypass the vehicle’s onboard charger and deliver direct current straight to the battery, enabling much faster charging times. Unlike AC chargers that are limited by the vehicle’s onboard charger capacity (typically 3.3–22 kW), DC chargers can deliver 50–350 kW or more, charging an EV battery to 80% in as little as 20–30 minutes.
This high-power delivery demands equally precise current measurement to ensure safe operation, accurate billing, and optimal battery management. Current sensors in DC charging stations monitor both the input AC current (from the grid) and the output DC current (to the vehicle).
LEM Current Sensor Solutions for DC Chargers
LEM provides a comprehensive range of current transducers specifically designed for the demanding environment of DC fast charging. These sensors must handle high currents (up to 500A), high voltages (up to 1000V DC), and operate reliably in harsh outdoor conditions.
HASS Series — Input Side Current Measurement
The HASS series of closed-loop Hall-effect current transducers are used on the AC input side of DC chargers. They measure the current drawn from the grid, enabling power factor correction and input protection. Key features include:
- Measuring range: up to ±1000 A
- Accuracy: ±0.5% of IPN
- Bandwidth: up to 150 kHz
- Galvanic isolation between primary and secondary
HTB Series — Output Side High-Voltage DC Measurement
The HTB series transducers measure the DC output current delivered to the vehicle. These sensors are designed for the high-voltage DC environment and provide the accuracy needed for billing-grade energy measurement.
- Measuring range: up to ±2000 A
- Accuracy: ±0.2% of IPN
- Operating voltage: up to 1500 V DC
- Temperature range: -40°C to +85°C
Integration and Safety Standards
DC fast charging stations must comply with multiple international safety standards. LEM current sensors are designed and tested to meet these requirements:
- IEC 61851-23: DC charging station safety requirements
- IEC 62196: CCS and CHAdeMO connector standards
- UL 2202: North American DC charging safety standard
- ISO 15118: Vehicle-to-grid communication protocol
By providing accurate, reliable current measurement on both the input and output sides of the charging system, LEM sensors enable DC charging station manufacturers to deliver safe, efficient, and billable fast charging experiences for electric vehicle owners worldwide.
