These include Full Hybrid Electric Vehicles (FHEVs), Plug-in Hybrid Electric Vehicles (PHEVs) and Battery Electric Vehicles (BEVs).
The modular SMU family has been designed to address the needs of designers of automotive battery management systems (BMS) who are looking to extend as far as possible the maximum driving range of an electric vehicle. The SMU continuously monitors parameters such as battery performance and safety systems and can identify anomalies and support diagnostics, helping to improve vehicle efficiency and ensure compliance with regulations.
The design of the sensor has taken into account the need for the smallest possible components so that EVs can weigh less and travel further on a single charge. The SMU measures just 29.1mm (H) x 35.5mm (W) x 49.9mm (L) while the busbar thickness is 2mm to 3mm compatible.
Maximising EV driving range requires an accurate State of Charge (SOC) estimation, which means precisely determining the remaining battery capacity. Accurate SOC estimation helps to optimise battery life and prevent unexpected power loss, while enhancing user confidence and delivering efficient energy management.
The SMU is a Hall effect technology sensor, open loop configuration using the latest LEM9 Application-Specific Integrated Circuit (ASIC). Designed by LEM to add intelligence at the Battery Disconnect Unit (BDU) level, the ASIC makes it possible to measure environmental factors while ensuring accurate sensor performance.
Several new features have been built into the SMU to optimise performance. For example, accuracy is improved by software algorithms that can correct or adjust measurement data to account for distortions or errors caused by mechanical stresses. This enhances the precision of the sensor's readings and makes it possible to reach 1% of accuracy up to 1300A and <1.7% up to 1500A. The current range of up to +/-1500A is ideal for BMS applications.
Other features include digital calibration, which provides end-to-end (E2E) protection, improved offset/sensitivity calibration, and such diagnostic warnings as under- or over-voltage. In addition, malfunction is avoided by a dedicated safe state mode should such issues as sensitivity and offset drift, temperature measurement errors, or memory errors (RAM, FLASH, EEPROM, ROM) be detected.
Also, the sensor’s internal microcontroller includes a built-in algorithm to correct for any magnetic offset, ensuring more accurate and reliable sensor readings by eliminating errors caused by residual magnetism.
The new sensor’s high isolation levels enable it to withstand voltage differences greater than 800 V between components or between the device and its surroundings. This improves safety and prevents electrical interference or damage.
Unlike other similar sensors currently on the market, the new SMU family is compliant with functional safety conditions. This means that it satisfies the stringent Automotive Safety Integrity Level (ASIL) requirements built into the ISO 26262 standard for functional safety in vehicles. The first version to enter the market is ASIL B ready with the possibility to extend it to ASIL C. ASIL B applies to systems where moderate safety risks are present, balancing safety with practicality in automotive design, and the new SMU family incorporates all the safety mechanisms and design processes that are required to address the risks associated with safety-critical automotive applications.
