Hybrid shunt and Hall-effect high voltage battery sensor for EVs
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LEM has launched a new current sensor for battery management in electric vehicles (EVs) that combines shunt and open-loop Hall effect technologies in a single part, called the Hybrid Supervising Unit (HSU), to meet the challenges of a small footprint, low-cost, and the highest safety level in the EV battery management system (BMS).
In an EV, the high-voltage BMS plays three key roles: it manages the battery’s state of charge and state of health, keeps the system and end-user safe, and performs cell balancing as part of the battery optimisation process. For higher safety levels, system engineers typically use a shunt resistor and a Hall-effect sensor to measure current.
Now LEM has combined the capabilities and performance of both technologies into a single unit, integrating it into the Battery Disconnect Unit (BDU). The signals from each section – the shunt and the current sensor – are then collected by the BMS. The current measuring range is up to ±2000 A at 10s for both parts, as is the wide operating temperature range of −40°C to +125°C.
The BDU switches high-voltage power to the EV on/off to enable different driving modes, including charging, driving, and regenerative braking, as well as providing safety functions.
At the BDU level, the HSU minimises footprint, weight, and cost (BOM), reduces integration effort for faster time to market, and enables easy system upgrades without impacting the mechanical layout while improving safety.
At the BMS level, the HSU enables system developers to reach the ASIL D safety level required for EVs easily.
The shunt’s resistance is very low at 25µΩ, and the Hall part is galvanically isolated, with accuracy of 2% at 500 A and 5% at 2000 A. Signal communication lines are separated into a shunt signal and an analogue or digital bus for the Hall part). An NTC (Negative Temperature Compensation) signal is provided for shunt temperature compensation.
Currently sampling, the HSU is the only component on the market with two technologies fitted into a standard shunt footprint. It is a plug-and-play unit, allowing easy mounting. LEM initially offers the HSU00 part, with HSU01 to follow in June. The two are suitable for the two most common BDU busbar sizes: 84 x 36 x 3mm (HSU00) and 84 x 20 x 3mm (HSU01).
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