Electromobility SMU sensor from LEM monitors the state of charge of various battery systems

Related Vendors

LEM International SA

Wuxi InfiMotion Technology Co., Ltd.

With its Single Monitoring Unit product family, LEM has introduced sensors that continuously monitor vehicle parameters such as battery performance and safety systems in hybrid vehicles and electric cars. The sensors also detect anomalies and support diagnostics.

The sensor design takes into account the need for the smallest possible components to keep the weight of an electric vehicle as low as possible. The Single Monitoring Unit (SMU) measures 29.1 mm × 35.5 mm × 49.9 mm, while the thickness of the busbar is 2 to 3 mm. The integrated busbar not only reduces the dimensions and increases accuracy, it can also accommodate busbars of different dimensions.

Direct imaging Hall effect sensor

The precise recording of the state of charge (SOC), i.e. the exact determination of the remaining battery capacity, is crucial for maximum EV range. A precise SOC estimate optimizes battery life and avoids unexpected power losses. The SMU is a direct-imaging Hall-effect sensor (open-loop) with the LEM9 ASIC developed by LEM. This increases the intelligence of the Battery Disconnect Unit (BDU), measures environmental factors and ensures accurate sensor performance.

Higher accuracy

Many new functions have been integrated into the SMU to optimize performance. For example, accuracy is improved by software algorithms that correct or adjust measurement data to account for distortions or errors due to mechanical stress. This ensures more precise sensor readings and an accuracy of 1 percent up to 1300 A and < 1.7 percent up to 1500 A. The current range of up to 1500 A is ideal for BMS applications.

Other features include digital calibration, which provides end-to-end protection (E2E), improved offset/sensitivity calibration and diagnostic warnings such as under or over voltage. In addition, malfunctions are prevented by a special safety mode if problems such as sensitivity and offset drift, temperature measurement errors or memory errors (RAM, FLASH, EEPROM, ROM) are detected. The sensor's microcontroller also has an algorithm for correcting magnetic offsets. This ensures more accurate and reliable sensor readings by avoiding errors caused by residual magnetism.

Functional safety

The insulation values of the new sensor make it possible to cope with voltage differences of more than 800 V between components or between the component and its environment. This improves safety and prevents electrical faults or damage.

Finally, unlike other similar sensors on the market, the new SMU series complies with functional safety regulations. The ASIL requirements of ISO-26262 for functional safety in vehicles are therefore fulfilled. The first version to be launched on the market is ASIL B-capable and can be upgraded to ASIL C. ASIL B applies to systems with moderate safety risks in which safety and practicality are harmonized in the vehicle design. The new SMU range includes all the safety mechanisms and design processes required to manage the risks associated with safety-critical automotive applications. (se)

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