Overview
Electric vehicles are transforming transportation, and at their core sit power electronics that must be accurate, efficient and safe. The battery pack, the traction inverter and the on-board charger all depend on precise, isolated measurement of current and voltage. The battery management system estimates state of charge and state of health from the pack current and voltage, the traction inverter controls torque from the phase current, and the charger regulates the charging current and monitors the battery voltage. LEM transducers serve all three, and BeiLuo supplies them with genuine traceability and FAE support.
Battery Pack Current Measurement
The battery management system measures pack current continuously to estimate how much energy remains and to protect the cells from over-current. Because those estimates integrate the current over time, even a small offset or gain error accumulates into a significant error, so low drift is essential. A closed-loop transducer such as the LA55-P measures bipolar current with low offset, which matters when the current crosses zero in the transition between charge and discharge. Accurate current measurement also underpins fast-charging algorithms and cell balancing, which depend on knowing exactly how much charge flows in and out of the pack.
State-of-Charge Estimation
State-of-charge estimation combines current integration with a battery model and, often, voltage and temperature measurements. The accuracy of the current sensor sets the floor on the accuracy of the estimate, because errors accumulate as the integral of the current error over time. Choosing a transducer with low offset and low thermal drift is therefore one of the most effective ways to improve the estimate without changing the battery or the algorithm.
Traction Inverter Phase Current
The traction inverter converts the battery DC into three-phase AC to drive the motor, and it regulates torque by controlling the phase currents. Fast, accurate current feedback enables field-oriented control with high bandwidth, which produces smooth, efficient traction. Closed-loop current transducers suit this role because they combine accuracy, low drift and fast response with the isolation the high-voltage inverter demands. Six transducers, or three with the appropriate range, cover a three-phase bridge, and each must be matched to the peak phase current of the drive.
High-Voltage DC-Link Monitoring
As battery voltages rise toward 800 V and beyond, monitoring the DC link safely becomes more demanding. The DVL1000 panel-mount transducer measures up to 1000 V nominal with a 1500 V range, and the compact DVC 1000-P measures the same class on a printed circuit board with a single +5 V supply and a direct output. Both provide galvanic isolation, which protects the controller and the operator from the high-voltage pack, and both deliver the accuracy needed for control and protection. Choosing the right mounting and isolation clearance for the pack voltage class is a key part of the design.
Designing for Automotive Reliability
Automotive electronics must survive vibration, wide temperature swings and long service life, so the sensing stage must be robust as well as accurate. Keep the primary conductor geometry as the factory calibration expects, screen the secondary signal from switching noise, and confirm the isolation clearance for the pack voltage. Choose the sensor package to fit the available space, whether that is a compact PCB module or a panel-mount part with stud connections. Where a design runs from a single low-voltage rail, a single-supply transducer such as the LTS25-NP or DVC 1000-P simplifies the architecture.
Selection and Supply
Selection starts with the current and voltage levels of the pack, the traction inverter or the charger, then narrows by isolation, accuracy, drift and mounting. Match the current rating to the peak with headroom, and choose the voltage transducer range with margin above the maximum pack voltage. BeiLuo keeps mainstream LEM current and voltage transducers in regional stock, ships them with import declaration, certificate of origin and RoHS documents, and supports selection, isolation planning and layout with an in-house FAE team. From the battery pack to the traction inverter and the on-board charger, our engineers help you choose the sensing that keeps the vehicle accurate, efficient and safe.