In the eternal quest for more efficient and reliable electric vehicles (EVs), breakthroughs in sensor technology are taking center stage. Recently, LEM unveiled a remarkable innovation, the Hybrid Supervising Unit (HSU), a current sensor that integrates two different technologies, shunt and Hall-effect, into a single package. This trailblazing device is setting new standards in EV battery management, thanks to its unique amalgamation of accuracy, speed, and isolation. Every EV’s lifeblood is its high-voltage battery pack, a complex system whose state of charge (SOC) and state of health (SOH) need constant monitoring. The battery management system (BMS) is the watchdog, ensuring the battery’s safety and performing cell balancing to optimize the driving range. Central to this operation is accurate current sensing, a task often divided between two different sensors: shunt resistors and open-loop, Hall-based current sensors. Traditionally, shunt resistors are responsible for handling 2,000 A of current. They guarantee higher accuracy and quicker response times, but they come with a caveat. They have to be placed directly on the copper wires or busbars that supply current to the load, thereby breaking the circuit. On the flip side, magnetic Hall-based sensors provide full isolation and enable contactless current monitoring, but their accuracy and speed are less than ideal. Enter LEM’s HSU, a sensor that deftly marries the best of both worlds. This integration achieves a fine balance between accuracy, speed, and isolation, eliminating the need to choose one over the other. Jérémie Piro, product manager for battery management and battery storage systems at LEM, notes that this integration “simplifies the system architecture, enhances safety, and allows for seamless upgrades without altering the mechanical layout.” The HSU’s design also contributes to cost efficiency by reducing the total bill of materials (BOM) and minimizing cycle time at the customer’s end. At the heart of the HSU is a shunt-based current sensor with a remarkably low resistance of 25 µΩ. This is coupled with galvanically isolated Hall-based sensing that provides 2% accuracy at 500 A and 5% accuracy at 2,000 A. The sensor also boasts segregated signal communication lines for shunt and Hall signals, with extra negative temperature compensation signals to fine-tune shunt temperature compensation. Specifically tailored for integration into the battery disconnect unit (BDU), the HSU is capable of managing power distribution from the battery to the powertrain and other EV components. The BDU effectively acts as an on-off switch for the high-voltage battery pack, and the HSU’s ability to cater to common busbar sizes makes it an ideal fit for this role. This innovative convergence of shunt and Hall-effect technologies into a single sensor, as accomplished by LEM’s HSU, represents a significant stride in the evolution of EV battery management. By striking a balance between accuracy, speed, and isolation, the HSU is poised to drive the future of electric vehicles towards a horizon of efficiency, reliability, and safety.
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