High-performance bus bar shunt resistors are helping electric vehicle (EV) designers meet the challenges of the market in new ways. This article reviews the basics of shunt-resistor technology and outlines several recent improvements, including a new metal-injection-molding process and a new form factor. These innovations are leading to breakthroughs in minimizing power loss, reducing physical footprints and managing thermal and conductivity properties.
Overview of shunt resistor technology
A battery in an EV must supply 100 kW of power or greater in response to driver demand. A typical EV battery system consists of hundreds of lithium-Ion battery cells connected in series to generate a voltage of 350 V or more. The voltage, current and temperature of the battery system must be carefully monitored to control charging and discharging, to balance the charge between cells, to keep the cells within their safe operating area (SOA), and to calculate key battery parameters such as state of charge (SOC) and state of health (SOH).
The current sensor must be able to accurately measure currents from milliamps to hundreds of amps over automotive operating temperatures of -40° C to 125° C and an operating life of up to 20 years. A shunt-based current sensing design determines the current (I) by measuring the voltage (V) generated as I flows through a shunt resistor (R) placed in the battery line, as expressed by Ohm’s law: V = I x R
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