[Solution Introduction] Using Rohde & Schwarz power supply to test battery management system (BMS)

Simulating, testing and measuring rechargeable batteries used in battery-powered devices and vehicles is critical. Overcharging and deep discharge shorten the life of rechargeable batteries. Design flaws can cause batteries to overheat or even catch fire.

Larger battery capacities are usually built by connecting in series and in parallel. Since all batteries are subject to the same charge and discharge current, individual differences in battery capacity, self-discharge, etc. cause the state of charge (SoC) to vary over time, limiting the capacity and life of the battery.

Balancing can be achieved passively by selectively loading the cell with the highest state of charge during the charging process or by actively transferring energy from the cell with the highest state of charge to the cell with the lowest state of charge using a switch-mode regulator.

Since the BMS plays a critical role in battery life and failure safety, it must be tested thoroughly. The tests must simulate all possible scenarios that may occur during operation.

The R&S®NGL200 and R&S®NGM200 DC power supplies from Rohde & Schwarz are universal devices that feature all the functions required to test and validate battery management systems.

The R&S®NGL200 and R&S®NGM200 support two-quadrant operation as source and load. They can deliver output currents up to 6 A and input currents up to 3 A. All outputs are fully isolated.

They can be connected in series to simulate a single-cell battery pack with a maximum voltage of 250 V to ground. The adjustable output impedance can be set from –50 mΩ to 100 Ω. The power supply displays the current and voltage values ​​at the output with high-resolution measurements.

All functions can be realized via remote control with a command processing time of < 6 ms. In addition, the R&S®NGM200 power supply series also has an optional battery simulation function that can simulate different predefined or user-defined battery types. In the ASCII file, the user can define the open circuit voltage and internal resistance for each battery type, which are parameters that affect the charging state.

These features allow simulation of the time-varying characteristics of the battery with high accuracy and high time resolution. For small and medium-sized batteries, the battery current can be directly output by the power supply. For larger batteries (such as those used in automotive applications), there is no need to actually charge and discharge them during BMS testing. The measurement results include the voltage value across the parallel resistor simulated to the BMS, and the power supply provides the battery voltage and balancing current.