Battery Management System (BMS)
A Battery Management System (BMS) is typically a battery pack composed of multiple battery cells. As a crucial link between the vehicle's power battery and the electric vehicle, the BMS's fundamental tasks are to ensure the safe and optimized use of energy within the battery and to provide accurate battery status information. Specifically, this includes: monitoring voltage, current, and temperature; automatically cutting off power in case of battery failure to ensure functional safety; balancing the battery cells within the pack; and providing battery status information for system communication. Among these functions, current sensing is a key component for achieving the safe, efficient, and stable operation of the battery management system.
Current sensing method
In BMS (Battery Management System), common current sensing methods include: the resistive shunt method, the Hall effect sensor method, and other magnetic induction techniques. The resistive shunt method works by connecting a resistor in series with the circuit load and calculating the current by measuring the voltage drop across the resistor. This method offers low cost and good linearity, and is suitable for both DC and AC current sensing.
Small size: Compared to other technologies, shunt resistors are passive components and are small in size, making them easy to integrate into PCB designs;
Excellent linearity and temperature stability: It exhibits good linearity and low drift performance under long-term use and different temperature environments;
Wide frequency range: Accurate measurement of currents from DC to several MHz;
Strong resistance to magnetic field interference: It is not sensitive to external magnetic field interference.
Bourns shunt resistors
In response, Bian Zhengjun, Senior Technical Support Manager at WT Microelectronics, a leading global authorized distributor of electronic components, recommended Bourns' shunt resistor products: "Bourns is a leading supplier of resistors, offering a complete range of resistor products, including chip resistors, chip resistor arrays, network resistors, and power resistors. Bourns provides a variety of resistor solutions for current sensing applications, and compared to similar products in the industry, its performance in terms of consistency and reliability is particularly outstanding, meeting the diverse application needs of many customers in the automotive electronics, telecommunications, industrial, and consumer markets."
For current sensing, Bourns offers a variety of resistor solutions covering different power, size, and accuracy requirements:
CR series: Standard thick film chip resistors with power ranging from 0.3W to 1W, suitable for general current sensing applications.
CRM series: Low resistance, high power current sensing resistors, supporting power from 25W to 2W.
CMP series: High-power/high-surge-resistance current sensing resistors with power up to 3W, suitable for applications handling high surge currents.
CSS series: High-precision, low-resistance metal strip resistors with power ranging from 5W to 12W, suitable for high-precision current sensing requirements.
CSM series: Compliant with AEC-Q200, resistance values from 25 to 100 µΩ, power range of 36W-50W, meeting the requirements of low voltage drop and high accuracy, supporting large currents up to 1000A, allowing thermal EMF as low as 25 µV/K and low TCR of 50PPM/°C, making it particularly suitable for automotive applications with high temperature fluctuations.
Bourns products are suitable for various BMS application scenarios and have the following excellent features:
Low resistance: Bourns' shunt resistors range from 25µΩ to 100mΩ, ensuring minimal voltage drop when measuring current, thus reducing power loss.
High power rating: Supports a power range from 3W to 50W, suitable for handling the high peak currents that may occur in a BMS.
Low temperature coefficient (TCR): as low as 50ppm/°C, ensuring that the resistance remains stable at different temperatures.
Low thermoelectric potential (EMF): Below 1µV/°C, reducing the thermoelectric effect caused by metal contact, suitable for high-precision current sensing.
Wide operating temperature range: The shunt resistor can operate stably in environments from -55°C to +170°C, making it suitable for BMS applications under extreme temperature conditions.
In addition, Bourns offers customization services, providing resistors with different shapes, hole arrangements, and sensing pin designs to meet the needs of various special applications.
Summarize
Future product design challenges include higher power density, operating temperature, operating voltage, and lower temperature coefficients. Bourns current sensing resistors are widely used in battery management systems, switching power supplies, and motor drives. Their low resistance, high precision, and high power characteristics make them ideal for current sensing in BMS applications. By selecting appropriate Bourns resistors, engineers can better optimize the performance of battery management systems, improving battery safety and lifespan. For more information on Bourns resistor products or to obtain professional technical support, please contact WT Wenye.
