LEM combines shunt and Hall effect sensing in 2000 A current measurement unit

LEM Electrical measurement technology specialist, has launched a new current sensing unit for battery management in electric vehicles (EVs). For the first time on the market, LEM has put together shunt and open-loop Hall effect technologies in a single part, called the Hybrid Supervising Unit (HSU), to meet the challenges of small footprint, low cost, and the highest safety level in EV battery management systems.

The EV’s 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 two separate devices, a shunt to measure 2000A and a current sensor fully isolated for measurements to 2000A.

Now, LEM has combined the capabilities and performance of both technologies into a single unit, integrating it into the BDU. The signals from each section – the shunt and the current sensor – are then collected by the BMS.

At BDU level, the HSU allows: Minimal footprint, weight, and cost (BOM); Minimised integration effort for faster time to market; and Easy system upgrade, without impacting the mechanical layout while improving safety.

At the BMS level, the HSU enables system developers to easily reach the ASIL D safety level required for EVs.

The shunt’s resistance is very low at 25µΩ, and the Hall part is galvanically isolated, with accuracy of 2% at 500A and 5% at 2000A. Signal communication lines are separated (shunt signal and analogue or digital bus for the Hall part), and there’s NTC (Negative Temperature Compensation) signal for shunt temperature compensation.

The current measuring range is up to ±2000A at 10s for both parts, as is the wide operating temperature range of −40°C to +125°C.

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).

Samples are available now.

LEM plans to expand its HSU lineup by introducing new technologies, for example, combining a shunt with a coreless Hall-effect part. The goal is to continue to shrink the devices’ size and cost while improving their performance.