As vehicles become more electrified and intelligent, the need for precise energy monitoring has never been greater. At the heart of this transformation lies a small but critical component: the battery current sensor. This article explores what it is, how it works, and why it plays a pivotal role in today’s automotive systems.
What is a Battery Current Sensor?
A battery current sensor is an electronic device that measures the flow of electric current into and out of a battery of an ICE, EV or HEV vehicle. It provides real-time data to the vehicle’s control systems, enabling accurate monitoring of the battery’s state of charge (SoC), state of health (SoH), and overall energy balance.
These sensors are based on Fluxgate, Hall effect or shunt resistor technologies. They convert current into a signal that can be interpreted by the vehicle’s electronic control unit (ECU) or battery management system (BMS).
Why are Battery Current Sensors Important?
Battery current sensors are essential for maintaining the efficiency, safety, and longevity of modern battery systems. Their key functions include:
- Monitoring charging and discharging cycles to prevent overcharging or deep discharging.
- Supporting start-stop systems by ensuring the battery has sufficient charge to restart the engine.
- Enabling regenerative braking in hybrid and electric vehicles.
- Providing diagnostic data for predictive maintenance and fault detection.
Without accurate current sensing, energy management becomes unreliable, leading to reduced battery life, performance issues, and potential safety risks.
Above all, a performing and accurate sensor at high voltage battery level allows precise SoC estimation and therefore a reliable driving range estimation, which is key for EV vehicles adoption by end-users.
How Does It Work?
Battery current sensors are installed on the battery’s negative or positive terminal, or integrated into the battery cable. Depending on the technology used:
- Fluxgate sensors detect the magnetic field generated by a primary current using a magnetically driven sensing element, leveraging changes in magnetic properties to measure the current accurately.
- Hall effect sensors detect the magnetic field generated by current flow and convert it into a proportional voltage.
- Shunt-based sensors measure the voltage drop across a known resistor to calculate current.
Advanced sensors also integrate temperature sensing, voltage measurement, and digital communication interfaces (e.g., LIN, CAN) to provide a complete picture of battery status.
Battery Current Sensing Applications in Modern Vehicles
Battery current sensors are now standard in a wide range of vehicles, from internal combustion engine (ICE) cars to fully electric vehicles (EVs).
Their applications include:
- Start-Stop Systems: In ICE vehicles, the sensor ensures the battery can handle frequent engine restarts without compromising performance.
- Battery Management Systems (BMS): In EVs and hybrids, the sensor feeds critical data to the BMS, which controls charging, discharging, and thermal management.
- Energy Recovery Systems: In regenerative braking, the sensor helps capture and redirect energy back to the battery efficiently.
- Onboard Diagnostics: Battery current sensors contribute to OBD systems by detecting anomalies in current flow, helping identify issues before they lead to failure.
LEM Battery Current Sensors: Precision for the Next Generation
As a global leader in electrical measurement, LEM offers a portfolio of high voltage and low voltage battery current sensors designed for the most demanding automotive and energy applications. Each product combines high accuracy, compact design, and robust performance.
High voltage battery current sensors
CAB Series - Best in class accuracy
- Accuracy up to 0.5% over full T°C range.
- Precise current sensing at 50mA offset.
- ASIL B and C readiness.
- Integrates with battery disconnection units or battery packs for xEVs.
- Compatible with 800V systems.
SMU Series – A wide measurement range in a versatile package
- Accurate State of Charge Estimation
- High Insulation Levels
- Temperature Resilience
HSU Series - The strengths of Shunt + Hall technologies combined
- Open loop sensor using Hall effect and Shunt
- High insulation level
- Primary current measuring range up to ±2000 A (10 s) both Shunt and Hall
Low voltage battery current sensors
HBCT Series
- Unipolar +5 V DC power supply
- Primary current measuring range up to −250 A / +100 A
- Maximum RMS primary admissible current: defined by battery pole to have T < +150 °C
LEM sensors are trusted by leading OEMs and Tier 1 suppliers worldwide, ensuring reliable energy monitoring in electric mobility and beyond.
The battery current sensor is more than just a measurement device — it’s a cornerstone of modern energy management in vehicles. From enhancing fuel efficiency to enabling electric mobility, its role is both foundational and forward-looking.
For engineers and system designers seeking precision, reliability, and innovation, LEM provides a proven range of solutions tailored to the evolving needs of the automotive industry.