DMC BMS Test Stands provide our clients with a comprehensive hardware and software platform for testing their BMS. The system is tailored to meet each of our customer's unique testing requirements, and is designed with flexibility to accommodate multiple BMS designs.
A combination of high performance off the shelf hardware components and custom subsystem components designed in-house by DMC are seemlessly integrated to build the system. Testing is controlled by a full featured LabVIEW application built around DMC's proven software architectures from previous battery test and measurement projects.
Details on specific subsystems and features of the BMS Test Stand are given below:
Cell Voltage Simulation
The BMS Test Stand simulates up to 108 battery cells (expandable to 216 cells with an optional secondary chassis), all of which are joined in series to create a full battery stack voltage of up to 750 V. With each simulated cell capable of outputting 0-7 V with 12 bit resolution (2 mV) and rapid voltage output response times, battery packs of varying chemistries can be effectively simulated.
Voltage and Current Measurement on All Simulated Cells
High precision measurements of the current draw on any battery cell or the exact voltage differential between any two cells can be performed, providing information that is very important in evaluating the operating characteristics of a BMS. DMC designed a custom low-cost multiplexing solution consisting of over 600 DC relays (1000 V), enabling a highly cost effective way to perform measurements on a high number of simulated cell channels using a single high precision PXI digital multi-meter.
Direct Manual Operation for Flexibility and Control
The BMS Test Stand software includes an intuitive user interface that allows operators to directly control all instruments, simulated outputs, and connections from the test stand to the BMS. This feature allows complete flexibility to subject the BMS to a broad combination of inputs and evaluate its response.
More information on the cell simulator design and specifications are available in this description of DMC's first generation BMS Test Stand.
Fully Automated Testing for Speed and Consistency
To fulfill our Client's requirements to perform a well defined set of testing procedures on the BMS, DMC integrates suites of fully automated testing procedures into the test software. A configuration interface allows the operator to set up a list of tests they wish to perform, the order in which those tests should be completed, and to enter whatever grading limit and setup parameters are appropriate for each given test procedure.
Once configured, a full functional evaluation of the BMS can be initiated with a single click. No further user interaction is required, and all PASS/FAIL results of the testing will be both displayed in real time on-screen and logged to file.
For more information on typical tests that may be automated in this fashion, see this Battery Testing White Paper.
Battery packs for electric vehicles (including the BMS itself) are subjected to a wide range of environmental conditions during real world operation, and thus extended duration environmental testing requirements are common. The configuration interface allows evaluation or monitoring procedures to be sequenced and cycled repeatedly to accommodate this style of longer term testing. The BMS operation can thereby be monitored while the BMS itself is exposed to demanding conditions within an environmental chamber.
For background information on the fundamental roles/functions of a BMS and the requirements/challenges in fully evaluating BMS operation, see this information on DMC's past BMS testing projects and this Battery Testing white paper.
Resistive Temperature Sensor Simulation
The BMS Test Stand standard configuration simulates 50 separate variable resistance temperature sensors to allow evaluation of all thermal monitoring functions of the BMS. Each sensor has 4 bits of resolution, meaning a total of 24 different resistance can be applied to each of the 50 simulated sensors. A modular architecture of swappable daughter cards containing different resistance values gives the flexibility to evaluate multiple BMS designs (which may each be built to interface with different thermistors). Optional system configurations can simulate more or less thermistors with lower or higher resolution.
CAN Unified Diagnostic Services
DMC leverages NI's Automotive Diagnostic Command Set API to provide CAN communication with the BMS under test using the UDS (Unified Diagnostic Services) protocol. This request-and-response based protocol, defined by ISO 15765-3, is commonly used as a standardized method of reporting of diagnostic information in automotive applications. Supported features include Read-Data-by-Identifier (Service 0x22), reading DTC info (0x19), Diagnostic Session Control (0x10), and Control Routines (0x31).
CAN Databases for Broadcast Messages
The system also allows acquisition and grading of typical broadcast data as defined by a user-specified CAN database file (e.g. *.dbc or *.ncd format).
CAN Traffic Logging
In addition to monitoring and evaluating whatever CAN data is of interest for each automated testing procedure, the testing software also performs real-time logging of all CAN messaging traffic on two separate CAN buses simultaneously whenever testing is in progress. Directly logging all CAN data transactions to disk provides the customer with a low-level record of the BMS state during all segments of testing and is a valuable reference when performing detailed analyses of failure points.
Battery Pack Contactors
Full battery packs include multiple high power contactors that connect/disconnect the battery stack from the vehicle's propulsion system. An important responsibility of the BMS is to handle opening and closing these contactors during vehicle operation, as well as to disconnect them whenever the BMS identifies a safety fault. The BMS Test Stand includes a battery pack contactor module that contains the same physical high power contactors that are used in the battery pack. Integrating these contactors into the simulated cell stack in the same configuration as in a full battery pack provides a more complete simulation of the BMS's "natural environment", which in turn allows more comprehensive functional testing to be performed.
System State Display
The test control software displays a graphical representation of the state of all subsystems, connections, CAN traffic, measurements, and instruments. This display is updated in real time during automated testing to provide visual feedback on the test stand activity.
Learn more about DMC's battery pack and BMS test systems expertise.