DMC worked with a major automotive OEM that needed to expand testing capacity for their new electric vehicle (EV) production line at their high-volume assembly plant. Their existing end-of-line tester was slow, inflexible, and deeply coupled with the overall line builder’s PLC workflow. Furthermore, the test provider had a proprietary test sequence editor that only they could support. This created a challenging dependency on a singular test provider for new features and updates to their test process. The OEM wanted to remove that dependency by using industry-standard testing tools and software platforms.

To add to the challenge, the OEM’s product development team was constantly revising their test requirements while simultaneously needing to begin building up their production test cells. We see this as a common trend among our customers: a race to get to market first, to capture market share and reduce overall product development costs. As a result, the traditional “waterfall approach” of developing a product and then creating a test solution around that prototype just takes way too long. With an agile/lean new product development approach, they are seeking to parallelize product design and software development with the design, build, and commissioning of the test systems required to validate their “still evolving” products.

DMC and our close partner, NI Emerson, were introduced to the OEM’s Test Engineering Team and recognized the customer’s challenges as an excellent opportunity to showcase DMC’s Battery Production Tester (BPT) framework, which is built on top of NI’s TestStand software platform. DMC had successfully used BPT as the foundation for numerous battery test projects over the past few years, so we knew it would provide the OEM with both the value and flexibility of NI TestStand, along with the simplicity and refined features they enjoyed in their incumbent battery test provider’s solution.

Replacing the incumbent solution turned out to be no small challenge, with many factors, including politics and familiarity with legacy approaches posed real obstacles for adoption of the DMC BPT. Ultimately, though, it was hard to argue with the results. DMC deployed our BPT platform on the first line, integrating seamlessly with the OEM’s existing hardware and controls while delivering faster cycle times, comprehensive test coverage, and complete data traceability.  The BPT platform allowed for rapid test development. Within 1 week of being onsite with the OEM’s new battery pack, the battery cycler, and the other test equipment at the customer site, DMC had a complete test up and running. The OEM told us that it usually took their previous test supplier over a month before the software framework was operational enough to run a full test on their packs, so this was clear value to them: ensuring the project stayed on track and met production timelines. It is also worth mentioning that DMC’s decades of battery test expertise played a critical role in helping the OEM overcome roadblocks with their BMS (battery management system) flashing process, which allowed us to provide the customer not only the tools but the expertise to quickly stand up a battery test line.

The result of our work together was a future-proof, software-centric solution that displaced a decade-long incumbent and positioned the OEM for scalable growth. DMC is now working with this same customer to deploy the BPT solution to over a dozen other EV and Plugin Hybrid EV (PHEV) battery pack production lines. The project has not only strengthened the customer’s battery test capabilities but also resulted in numerous updates, improvements, and hardening of DMC’s BPT platform, which we’re excited to share with other customers looking to optimize their battery test operations.

Figure 1: DMC’s Battery Production Test (BPT) Software. Shown Screen: BPT’s low-code BPT Socket Test Overview Screen

Customer Benefits

• 13% Faster Test Cycle Time – Increased throughput, without adding additional test stations. This optimization occurred over the span of 1 month, compared to the optimizations that the incumbent had been implementing for years.
• Multi-DUT testing – With parallelization capabilities and BPT’s enhanced multi-up configuration UIs, it’s easy to design your test sequence for one DUT but test on multiple sockets for improved utilization of capital-intensive equipment like high-power battery cyclers.
• Seamless Integration – The BPT solution fits into existing production line architectures with minimal hardware changes. The BPT HAL (hardware abstraction layer) allows for supporting different brands and models of PLCs, cyclers, and other devices and instruments required for a test. No new capital expenses are required to swap out the existing test system hardware!
• Centralized Configuration & Deployment – Push software, configuration, parameter, and grading updates across stations and easily reuse test sequences on new battery pack models.
• Expert Support – DMC’s engineers helped resolve BMS flashing issues and debug the customer’s product software to meet their production deadlines
• Comprehensive Test Coverage in a Modular Form Factor – Electrical, BMS, and power capability tests in one station, or split across numerous lines for improved takt time. DMC’s BPT software is modular and supports one “do-it-all” test station or deployment across numerous, tightly scoped test stations to increase throughput. Simply select your station type and BPT manages all the configured devices/instruments and available test files for you!

Figure 2: Station Type configuration file organization

Figure 3: Test Station configuration User Interface

Technologies

Hardware:

• NI cDAQ chassis
• Industrial PC
• NI RMX power supply
• Battery cycler (any brand/model)
• PLC (Rockwell / Siemens)
• Safety interlocks, RFID scanners, thermocouples, etc.

Software:

• DMC Battery Production Test (BPT) platform
• CORTEX framework (DMC’s NI TestStand-based test executive)
• CAN, Modbus, Ethernet/IP, Automotive Ethernet, MES, MQTT, SystemLink integration modules and more!
• Custom, low-code overview screen
• Live waveform visualization and manual mode diagnostics
• DUT Variant Parameterization: Allows reuse of a single test sequence for multiple DUTs with different test limits or other test variations
• Separated engineering IDE and operator UI for distinct workflows

Solution

The Battery Production Tester (BPT) platform is a software package, built with NI LabVIEW and on top of NI TestStand. The software was designed with two primary users in mind:

• Test Operators: People working on the production line who need a simple user experience to understand what is happening on the line and make modifications if needed
• Test Engineers: Experts on battery test who want to design optimized test sequences quickly to test new products or identify potential product defects.

To accomplish this, BPT has a “BPT Application” component that is deployed on each test station, as well as a “BPT Engineering Environment” component that is used by engineers on their development laptops. From this environment, engineers can fully configure a test station remotely, push their changes using industry-standard version control tools, and track changes made to test configurations.

The BPT Application provides rich user interfaces that show live data in summary views and waveform graphs and display parametric test results in a modern UI. Operators have access to a limited subset of functionality, depending on the user role and permissions assigned to them, either locally managed or IT-linked LDAP.

The BPT Engineering Environment provides engineers with all the power and capability that NI TestStand offers, without the complexity of setting up the TestStand infrastructure. BPT has simple configuration dialogs for all the main settings and convenient parameterization that engineers often need to test a battery pack efficiently. These smart features greatly simplify the engineering workflow compared to starting over from scratch each time. Furthermore, DMC exposes a rich and expanding library of common battery test devices and instruments (including CAN, Automotive Ethernet, Power Supplies, DI/DO/AI/DO, Modbus, EthernetIP, etc.). These sequence steps provide high-level, configuration-only building blocks that engineers can drag and drop into their test sequence. Each step can have a unique Testpoint assigned to it, which allows easy traceability into which test steps are failing most often, something your quality team cares deeply about.

Figure 4: BPT Application – Test Sequence Execution View

Figure 5: BPT Engineering Environment (Built into NI TestStand via Extensions)

The BPT platform also supports centralized configuration management, allowing engineers to push updates to multiple test stations simultaneously. By single-sourcing sequences and parameterizing them across different DUTs, the customer dramatically reduced the engineering effort required to maintain and scale their test systems.

For this project, we customized DMC’s BPT to work seamlessly with the OEM’s existing test cell setup — including their chosen battery cycler and assembly line PLCs. Thanks to BPT’s modular plugin system, making those connections was straightforward. The hardware abstraction layer (HAL) also positions the OEM to easily swap out instruments and optimize their hardware expenses in the future – without major rewrites to their test sequences. This flexibility ensures long-term adaptability as the OEM continues to evolve its battery production strategy.

The software ran a full end-of-line test that checked electrical performance, ran BMS diagnostics, and verified hi-power charge and discharge capabilities. All the results were automatically saved and sent to a central database for easy tracking, while preserving local copies of the test results for immediate viewing on the test station if needed. The automated test software ran without any human-in-the-loop, triggered by a line PLC. The BPT UI screens gave the operators a clear understanding of what was happening with the test system and  provided them with the necessary tools to step in and troubleshoot the system when needed. The engineering team could watch the test results stream in live from their SystemLink connection, making access to the test data easier than ever to retrieve and analyze.

BPT Features

Built on the CORTEX framework, DMC’s BPT platform delivers robust and scalable test architecture tailored for battery production environments. It includes many valuable features, including:

• Open, standards-based software architecture: Unlike proprietary test systems that lock users into vendor-specific tools, DMC’s BPT is built on NI TestStand — an industry-standard platform. This gives the OEM complete control over test sequences, enables easy integration with third-party hardware, and ensures long-term flexibility without vendor lock-in.
• Standardized Sequencing – Built on NI TestStand with a custom Sequence Editor and reusable step libraries, enabling engineers to develop and maintain tests efficiently using industry-standard tools.
• Hardware Abstraction Layer (HAL) – Abstracts instruments and devices through plugin classes, supporting DMMs, DAQ, serial and industrial protocols (Modbus, Ethernet/IP, Automotive Ethernet), power supplies, PLCs, and more. This allows the customer to swap out hardware as needed without rewriting test sequences.
• Configuration Over Code – Dynamic workspaces, station configurations, and device-socket mapping enable engineers to configure multi-up stations and test logic without deep programming expertise.
• Production-Grade User Experience – Includes Auto and Manual test modes, device dashboards, live channel viewer, alarms, and role-based user permissions. Operator and engineering interfaces are separated to support distinct workflows.
• Reporting & Traceability – Combines parametric test reports with engineering waveform logs (TDMS), enabling root cause analysis and complete visibility into test execution.
• Ecosystem Integration – Seamlessly connects to PLCs, MES systems, custom databases, and IT infrastructure (e.g., LDAP for user management), ensuring the test system fits into the customer’s broader manufacturing environment.

Figure 6: Live Waveform (Data Server Viewer)

Figure 7: DUT Parameters Editor for configuring variables on specific product models, enabling reuse on a shared test sequence

Figure 8: DMC BPT Results Viewer Tool that combines TestStand Report Results with Continuously Acquired Data

Let’s Start a Conversation

Looking to modernize your EV battery testing process? Have specific concerns for your battery test project? Wondering if BPT can help your team? DMC’s BPT platform delivers speed, flexibility, and deep test coverage, without disrupting your existing production line.

Contact us today to learn how we can help you scale your battery manufacturing with confidence.

The post Powering Up an EV Battery Production Line with DMC’s BPT Platform appeared first on DMC, Inc..

Software for battery test execution was programmed in LabVIEW for Real-Time to capitalize on deterministic performance and stand-alone reliability.  A PXI chassis with a Real-Time operating system provides critical control logic and data acquisition.  Each chassis is capable of running 10 asynchronous tests for 1000 hours or more.  The test chassis are on a local network, and store data to a central file server running an MS Windows Server and an SQL Server.  Any test on the system can be configured, controlled, and monitored from any PC on the network.  The custom Test Interface features the ability to define test steps, configure modular hardware, access a Battery Information database, and monitor live test conditions.  Raw data is stored in a TDMS format and is viewable through a custom data viewer and NI DIAdem.

Battery and Fuel Cell test environments can present significant safety concerns.  A lab-wide safety system consists of independent, highly available cRIO devices that monitor lab conditions and are capable of automatically shutting down tests in case of hazardous lab conditions.   This functionality is achieved with LabVIEW for Real-Time and for FPGA.

The system provides a modular, scalable, and fully configurable test platform, allowing the engineers and scientists at Argonne to accommodate and accurately test a wider variety of energy storage devices.  The high level of flexibility delivers precise test results without requiring the use of any one specific battery cycler hardware device.

Learn more about DMC’s Test & Measurement Automation expertise and contact us for your next project.

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Test Specification

The functional test specification required:

• BMS firmware flashing
• Cell emulation
• Thermistor emulation
• Temperature and voltage tests
• Communication over CAN and serial buses
• Analyzing LED status indicators

Each BMS test results in a report with metadata identifying the DUT, test system configuration, and test results with limits included.

Systems Engineering

DMC had to factor in many requirements including test accuracy, cycle time, operator ergonomics, and overall system envelope. DMC leveraged our internal fabrication shop and carefully selected external vendors like Pickering for robust hardware solutions. The software design leaned on DMC’s existing platforms and tools to minimize costs while maintaining performance and reliability.

DMC divided the hardware design into modular sub-systems: data acquisition box, Bed-of-Nails test fixture, and instrument rack. The rack design housed multiple Pickering LXI chassis containing cell simulation and thermistor cards. The interfaces between these sub-systems were well defined early in the design process, along with consistent communication to minimize design siloing.

Software Design

Software customizability was a major consideration for the client, DMC built upon its proven Battery Production Test (BPT) platform to meet client’s software requirements. Some highlights include:

• Intuitive user interface and user experience design
• Customizable test sequences through NI TestStand
• Traceable reports with MES integration
• Tracked and version-controlled test configurations (workspaces)

Conclusion

DMC delivered a robust and highly configurable system on a deadline, providing our client with BMS test capability ahead of their full battery pack assembly line. The solution detects manufacturing defects and provides traceable test results to each battery under test.

Learn more about DMC’s Battery Production Test (BPT) System, check out this BMS Power HiL Test System, or contact us to discuss your next project.

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DMC started this project with a clear request to provide a BPT-based system within the Client’s strict budget.  DMC carefully analyzed their battery pack design, interfaces, and operating modes, and their overall testing requirements. This analysis revealed that the Client’s battery pack interface was relatively low-complexity, and their initial testing needs were rather basic. Since their requirements did not necessitate the use of DMC’s more full-featured BPT composition (see this case study), we initiated a new, lower-cost design, leveraging existing DMC hardware control modules. The result was a simple modular concept for achieving the basic battery pack tests that this Client required, while also meeting their aggressive budget demands.

This basic, but very cost-effective, BPT implementation allowed the Client to optimize use of their capital budget by purchasing only the test capability they needed for their current product. However, since this solution leverages the BPT platform software and NI hardware, they can still achieve the flexibility required for later expansion if needed.

Hardware System

To achieve this new BPT design, DMC leveraged the modularity of the NI platforms that form the basis of the BPT software and hardware system. Switching out the more capable, but also more costly, NI PXI systems for very cost-competitive NI cDAQ platform modules was easily accomplished with the NI DAQmx interface. DMC quickly transitioned our larger and more flexible BPT Low Voltage battery pack interface to a more basic one for control of all the required interfaces of a typical automotive battery pack: Vbat, IGN, GND, HVIL, CAN (see Figure 1). Similarly, DMC converted our larger and more complex ‘High Voltage Contactor Module” into the smaller and simpler sub-system shown in Figure 2.  While the resulting hardware system would have easily fit into a smaller test system rack, the Client wanted to reserve room for future expansion and selected a 36U high test rack, as shown in Figure 3. 

Software System

While the BPT hardware system was optimized for cost though selective hardware design, the software system of BPT was simply expanded to allow full control of the new low voltage and high voltage hardware sub-systems.  As such, users of this more cost-effective BPT system still have full access to the rich BPT software feature set, and full testing capability, including:

• Test Execution Management.
• Test Sequence programming using NI TestStand (Figure 4).
• Automatic and Manual run modes (Figure 5).
• Control of DMC hardware modules using pre-configured TestStand Custom Steps.
• Easy to use NI XNET CAN interfaces.
• Automated and customizable Test Results Reporting.
• Optional Custom Overview and Data Display Screens (Figure 6).
• Optional System Link integration. (Figure 7).
• Optional MES and Server Integration.
• Optional interface for common PLC communication protocols.

Conclusion

This new BPT model perfectly fit the Client’s battery pack test requirements, and their business needs:  Providing maximum test value, with optimized capital spend, and room for future expansion.

Learn more about DMC’s Battery Production Test (BPT) System and Custom Battery Pack and BMS Test Systems or contact us to discuss your next project.

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DMC developed a power Hardware in the Loop (HIL) simulator, which allows the client to safely simulate different battery conditions that are difficult and potentially dangerous to do with a real battery pack. The system allows the client to do a variety of testing to validate the design of their BMS before using it for full scale vehicle testing.

When the client runs a simulated flight with their drone, the DMC system simulates the battery pack operation throughout that flight, allowing the client to simultaneously test the BMS and power electronic system’s response to that battery during the simulated flight. Optionally, the client can simulate the occurrence of specific battery fault conditions (open/short/reversal) during a simulated flight, to ensure the BMS and flight systems detect, report, and manage the fault appropriately.

The developed HIL system is a complex but modular assortment of off-the-shelf and DMC custom hardware. To simulate the voltages of all the individual cells in the battery pack, DMC used a Pickering LXI Chassis loaded with Pickering PXI Battery Cell Simulators. We also used Pickering PXI cards in the LXI Chassis to simulate the battery pack’s internal temperature sensors/pack current sensors were simulated using NI c-series modules located in a cRIO Chassis.

While the individual cell voltages to be monitored by the client’s BMS were simulated by the Pickering PXI cards, they do not provide sufficient power to supply the drone’s power electronics and motors. The actual battery stack voltage, current, and power sufficient to drive the drone’s power electronics and motors is provided by Keysight RP7900 Series Regenerative Power Supplies. The DMC power HIL system synchronized the voltages of the Pickering Cell simulators with the Keysight power supplies within a few milliseconds, even under various faulted conditions.

While the hardware listed above is capable of completely simulating the battery pack, the client required the ability to simulate several faults that could occur during assembly of the pack or during vehicle operation. This capability would allow them to conduct tests to ensure the drone safely handled all faults prior to putting it in the air.

To provide this functionality, DMC designed and developed three custom fault injection boxes. DMC’s Test and Measurement team specified the control system, modular interface, and functionality of these boxes. DMC’s Embedded team designed the custom circuit boards required for the fault boxes to simulate different fault conditions for the battery cells. With this subsystem, the client can select to place any combination of cells into one of four states: no fault condition, cell reversed, cell short circuited, or cell open circuit.

For the control system of the power HL system, DMC chose NI VeriStand. VeriStand is a powerful, but user-friendly platform for HIL systems and provides simple and robust control of all the required hardware. VeriStand uses an industrial PC running the Windows operating system to act as the system HMI and programming console. The VeriStand control model runs on an embedded real-time controller (NI cRIO), so it can easily handle the high-speed I/O and simulation loops required in this system. The client also made skillful use of the basic sequence editor built into VeriStand, allowing them to create simple sequences for their testing needs: such as injecting faults on specific cells or performing manual control of outputs.

DMC created a simple electric circuit model for VeriStand so that the battery voltages would respond to the current draw of the client’s power electronics in exactly the same manner as the actual battery cells. This allows the client to simulate scenarios such as terminating a flight based on a low battery pack state of charge (i.e. running out of fuel).

The model also adjusts the simulated temperature of the cells based on the measured battery usage, so the simulated thermistor outputs react exactly as expected when the battery is charged and discharged. This allows the client to test conditions in which the battery temperature goes out of range. The battery model parameters are adjustable by the clients, so any change in cell chemistry can be handled by simply entering new parameters in VeriStand and restarting the simulation.

To house all the hardware needed for the test stand, DMC’s test and measurement team completed a small rack enclosure design for housing the various components in a manner that allows ergonomic use of the test system and easy access to components for any required service.

DMC’s Control Panel Design and Fabrication experts from the DMC Fabrication Studio assembled the test system’s rack, subsystem components, and custom fault boxes. They also completed the final wiring of the system. Building the test stand in-house allowed for an efficient assembly, and quick resolution of any issues that required alterations and/or adjustments during IO checkout and Factory Acceptance Testing.

DMC’s experience with custom circuit board building and the use of our Fabrication Studio allowed us to provide the client with quick assembly of the test stand and a quick turnaround time when making improvements, modifications, or adjustments.

Our client can now simulate and emulate the performance of their battery pack under a full range of normal and faulted conditions, allowing them to fully test and validate the safe operation of their autonomous air delivery vehicle.

Learn more about our Battery Pack and BMS Test Systems expertise and contact us today for your next project.

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Six stations are used on the manufacturer’s two production test lines. Each line of three BPT stations shares one bank of NHR cyclers operating in parallel. A high power multiplexing (MUX) panel allows for this cycler sharing and includes infrastructure for each line to be expanded to by an additional station, allowing for up to four stations per line. The seventh station is a dedicated rework station.

High level overview of a single production test line where a MUX Panel allows up to four BPT stations to share a single bank of cyclers. DMC Delivered two of these test lines.

High level overview of Rework station, where the BPT station is connected directly to a dedicated bank of cyclers.

DMC provided additional custom hardware features, including a High Power Contactor Panel design that meets the specific needs of the client’s battery pack, and custom software features, including integration with the client’s manufacturing execution system (MES) to manage test execution and report test results.

Functional End of Line Tests

The BPT platform leverages NI TestStand to run a suite of production test sequences. For this application, the functional test sequences DMC developed include:

• BMS communication check
• Firmware flash
• Low voltage current check
• BMB communication check
• BMS sleep current check
• Pressure sensor check
• Brick voltage check
• Temperature sensor check
• Humidity sensor check
• Pack current sensor check
• BMS addressing check
• HVIL functionality check
• Contactor weld check
• Contactor control voltage check
• Pre-charge with open load check
• Pre-charge with shorted load check
• Pre-charge with good circuit check
• Isolation resistance check
• Induced isolation fault test
• Internal CAN check

In addition to the functional tests, DMC also developed sequences that utilize the NHR cyclers. These sequences include:

• Burn-in discharge test
  • Run at the end of the functional tests
  • Discharges pack at peak rated current for a relatively short duration
  • Measures electrical losses and thermal performance at maximum power delivery
  • Discharges pack to shipping state of charge (SOC)

• Charge to build SOC
  • Charges pack back to build SOC for retest / rework purposes

Cycler Sharing

DMC designed and implemented a high power multiplexing (MUX) infrastructure to connect a single bank of NHR cyclers to up to four test stations. This allowed the client to capture significant hardware cost savings, since a separate bank of cyclers was not required for each test station.

Overview of multiplexing design that allows up to four BPT Stations to share a single bank of cycler.

DMC designed the high power MUX panel with hardware lockout relay logic to prevent multiple stations from attempting to use the cycler bank at the same time. This lockout logic ensures that if a single station commands the contactors in the MUX panel to connect the cyclers to the station, the circuits to connect power to any other contactors coils are interrupted. Therefore, when a single station reserves the cyclers, no other stations can connect to the cyclers. Once a station finishes using the cyclers, it releases the cyclers and MUX panel so that other stations may reserve the cyclers.

Image of MUX Panel bus bar and contactor infrastructure.

DMC included a software configurable timeout to trigger an alarm and report to the facility MES system if a station waits too long to gain access to the cyclers. This feature allows the client to identify potential process improvements to ensure that packs are tested efficiently across the multiple stations on a single test line.

Additionally, DMC’s design allowed for the MUX panel to be included into the production test line’s emergency stop (Estop) circuit such that any one station can Estop the MUX panel (open all contactors) and cyclers, and the cyclers are able to Estop the MUX panel and all test stations.

Customized High Power Contactor Panel Design

Once a station reserves the cyclers and is connected to the cycler output via the MUX panel contactors, the station controls additional contactors within the High Power Contactor Panel mounted in the station rack to connect the cycler through to the battery pack under test.

Connection between bank of cyclers and battery pack under test via BPT High Power Contactor Panel.

The platform or “baseline” design of the BPT High Power Contactor Panel includes contactors that are used to make the final connection from the cyclers to the battery pack.

DMC customized this client’s High Power Contactor Panel to introduce other high voltage electrical components into the circuit, per client needs. In this case, the High Power Contactor Panel includes:

• Resistor-capacitor (RC) circuit
  • This RC circuit mimics the impedance of a vehicle powertrain inverter when connected to the battery terminals.
  • This circuit provides the necessary conditions for the battery pack BMS to accept commands to close its internal contactors.
• High current fuse
  • This high current fuse allows for a “short circuit pre-charge” functional test where the test stations close the appropriate contactors in the High Power Contactor Panel to short battery pack’s terminals across the fuse while the pack’s internal contactors are open. The station then attempts to command the pack to close its internal contactors.
  • The purpose of the test is to ensure that the pack’s battery management system (BMS) recognizes the short circuit and does not close the pack’s internal contactors when commanded while there is an unsafe short circuit condition.
• Polarity swapping infrastructure
  • The client manufactures multiple battery pack variants. On some pack variants, the battery terminals are arranged in a reverse polarity configuration.
  • The High Power Contactor Panel includes contactor and bus bar infrastructure to appropriately connect the battery terminals to the correct side of the cycler output according to variant polarity.
  • This infrastructure includes a lockout relay so that both polarity selections cannot be made at the same time.
• High voltage sense points
  • This variant of the High Power Contactor Panel includes six high voltage sense points that are connected back to the measurement matrix. This allows the voltage sense points to be measured by the system digital multimeter.
  • These high voltage sense points can be used to measure the voltage output by the cycler, measure the voltage of the battery pack, ensure the battery pack is connected with the correct polarity configuration, and verify the states of the various contactors in the High Power Contactor Panel for system self-diagnostics purposes.

Custom High Power Contactor Panel design.

MES Integration

DMC integrated with the client’s manufacturing execution system (MES) system to manage test execution and track test results. This MES integration utilizes the NI HTTP Client toolkit to interact with the client’s REST API.

Test Execution Management

Upon entering a test mode, the BPT system queries the client’s MES to determine whether sample testing is required. This allows the client to define a set schedule on which sample testing must be performed. For example, the client may choose to run a sample test at the beginning of each shift, day, week, etc. If sample testing is required, the BPT system alerts the test operator via a popup dialog.

The test operator is then prompted to scan the barcode on the pack under test. The BPT system parses the barcode to extract the serial number of the pack under test and queries the MES to determine whether the pack is ready to be tested. If the pack is not ready to be tested, the operator is alerted via popup dialog, and the test is terminated. If the pack is ready, the operator is allowed to continue with the test. The sequence to be run on the pack is automatically selected based on the pack part number, which is also parsed from the barcode scan.

Test Results Reporting

In addition capturing test results in a TestStand report document, the BPT system collects and publishes test results to the client’s MES. Results include individual graded measurements, higher level test results (e.g., BMS communications check pass or fail), major test results (e.g., Functional Test pass or fail), and overall “global” test result (i.e., whether the pack passed all tests or failed).

Rework Station

In addition to this client’s six test stations for two production lines, DMC delivered a seventh test station to be used for testing battery packs that may need to be re-tested, repaired, or reworked. For example, if an issue is identified with a battery pack during the first pass of production testing, it could be pulled off the main production line and re-retested with a more detailed diagnostic test routine to identify the issue and determine a rework or repair strategy.

The rework station highlights the flexibility of the BPT platform. All seven of the test stations are identically built and run the same software. The stations include all the necessary hardware, signal capabilities, and software features to complete both standard production testing and rework testing. The BPT’s simple hardware configuration capabilities and its Manual Mode feature enable this flexible testing.

Hardware Configuration

Since this rework station has its own dedicated bank of cyclers, the software includes a simple method for specifying the hardware configuration using TestStand Station Global variables. These are used to determine whether a station has its own dedicated cyclers or shares cyclers so that the cycler sharing logic can be included or omitted accordingly.

Manual Mode

Another software feature that is particularly valuable for rework testing is the Manual Mode test mode. Notably, only users who log in with advanced credentials can access Manual Mode. Standard users do not have access to this feature and can only run tests in Auto Mode.

As the name implies, Manual Mode allows an advanced user to interact more manually with a connected battery pack, as opposed to just running the pre-determined test sequence. Key features of Manual Mode include the interactive System State diagram and the Device View.

Interactive System State

The System State provides a convenient interface to view the current state of the system’s hardware. The System State includes:

• User-configured signal aliases
  • Allow the user to assign logical names to physical pins.
• Connector pins
  • Provide pinout information to correlate user-configured aliases with physical pins.
• Relay controls / indicators
  • Display the current state of relays at any given point during a test and allow the user to manually control relays.
• Instrument connection points
  • Show how the system instruments are integrated with the switching infrastructure.

The visualization of this information allows users to quickly understand the current configuration of the system and the possible paths that can be achieved with the BPT’s flexible switching infrastructure.

In Manual Mode, the System State diagram is interactive such that a user can click to command the various relays in the system to make pathing connections for diagnostic purposes. Additionally, in Manual Mode, the user can directly command the instruments in the system using the Device View.

Interactive System State.

Device View

In Manual Mode, the Device View allows the user to drag and drop soft front panels for the devices in the system. This functionality allows the user to build their own custom device “dashboards” to monitor and control the state of the instruments in the system.

As a simple example of how the user could leverage Manual Mode for diagnostic-style testing, the user might command relays on the System State to connect a battery pack signal to the system digital multimeter and then use the digital multimeter soft front panel in the Device View to measure voltage on that signal line.

Conclusion

DMC built upon the flexible Battery Production Test platform to deliver seven turnkey test stations. The standard battery test capabilities of the BPT platform in combination with the hardware and software customizations DMC implemented for client-specific requirements enable the client to efficiently and reliably test their electric vehicle battery packs.

Learn more about DMC’s Battery Pack and BMS Test Systems and contact us for your next project.

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Unico builds leading-edge variable speed drives and controls systems for companies on the cutting edge of new technology. They are among the leading automation companies in this space with proven experience spanning over 5 decades. More recently, Unico has taken this expertise into the automotive industry, where they continue to expand their drive systems for testing vehicle powertrain designs today and the EV propulsion systems of tomorrow.

One of their central offerings in the automative space is their EV battery cyclers (Figure 1), which clients of theirs use to perform high voltage electric vehicle testing procedures on battery packs and modules. These cyclers provide clients the ability to perform battery packs test cases (i.e. charging, discharging, periods of high current draw and recharge, etc.), whilst also exposing a myriad of serial interfaces for control of the system.

Despite these features, some of Unico’s clients simply lack the technical expertise to design and build control systems that could easily integrate with their cycler and allow them to readily use it out-of-the-box. In such cases, clients would rely on unplanned Unico support hours or external system integrators to use their cycler, inevitably driving test system costs upwards.

To combat these startup issues, Unico reached out to DMC to create a suite of user-friendly device drivers in LabVIEW that would ship with their battery cyclers.

End User Benefits

The creation of this driver set would empower purchasers of the Unico cycler to easily create control systems within the NI software framework to control/monitor their devices with minimal development or setup. This would not only ensure that Unico’s existing customers would save time and money with these drivers at their disposal, but could also potentially drive new business for Unico, as the driver set provides the flexibility of incorporation into a wide array of technical applications, while simultaneously lowering the technical experience needed for a customer to use their cycler right out of the box.

Why DMC?

Unico chose DMC for this project based on several factors. DMC is one of only a few NI partners designated as a National Instruments “Center of Excellence,” demonstrating extensive experience in NI hardware and software solutions, including complex vision, end-of-line, and automated testing applications. Importantly, DMC has been in the battery testing industry for over 2 decades and has an in-depth understanding of end user requirements.

As NI’s Primary Battery Test System (BTS) integration Partner, DMC has been collaborating with the NI team to expand DMC and NI’s battery test software platforms to collaboratively ensure NI-based solutions reach as many customers as possible in the fast-moving and fast-growing EV market. For Unico, this presents an exciting opportunity to become seamlessly integrated into the NI software suite, allowing automotive manufacturers or battery test laboratories using NI software to feel as confident as possible when opting to purchase Unico cyclers.

The Solution

DMC created a functional set of object-oriented API methods in LabVIEW, encapsulating the various commands a user might want to make when interface with their cycler. Alongside these, DMC also created lifecycle APIs, controlling the construction, initialization, termination, and disposal of the Unico cycler class object. A brief description of these APIs is provided below:

Technical Details

Given this is an object-oriented driver set, it is important to note that the only method in which a child class implementation needs to be used is the Construct method. This is due to the fact that it creates the appropriate class object once constructed, which gets passed throughout the calling program, allowing the APIs called later down the line to dynamically dispatch down to their appropriate child implementations. The specific child implementations of the Unico cycler class object represent the various serial protocols through which communication between a PC and the Unico cycler may be occurring. At the moment, the only implementation is through Modbus TCP, but the driver set has been created in a way that would make it easy to create a new child class implementation to account for a different communication protocol.

Another important thing to note is the safety features of this driver set. While, inherently, this software will not be responsible for the majority of the safety logic implemented within the Unico cycler firmware and hardware, there are features in place to ensure that errant usage of the driver set does not compromise the safety of those using it. For example, our Initialize method ensures that we read and store the rated voltage/current limits of the cycler in use, allowing our drivers to generate errors if users attempt to configure software voltage/current operational limits outside of the hardware rated limits.

One input into our Construct method is Min Threshold V, which defines the minimum allowable voltage difference between the measured voltage of the DUT and the internal cycler voltage before internal contactor of the cycler can be closed. Of course, a natural firmware limit to this value is enforced through the Unico firmware, but a user can configure this minimum threshold voltage to be even lower, thus further preventing arcs and large inrushes of current onto the system, minimizing potential damage to and early degradation of the battery cycler and DUT.

Our Initialize method also kickstarts an asynchronous loop upon establishing a successful connection with the Unico cycler, which is responsible for routinely polling, writing commands to, and maintaining a bidirectional watchdog/heartbeat with the battery cycler. The loop rate of this asynchronous process (Asynchronous Loop Time) is completely configurable, as it is also an input to the Construct method. Once the cycler driver class is initialized, a user can also customize the Watchdog Loop Time, which is the amount of time needed without the battery cycler receiving a modulated watchdog/heartbeat bit to display a timeout fault, using the Command Watchdog Loop Time API. We ensure this value must be commanded to be at least 4x the Asynchronous Loop Time, as the rate at which our driver is sending heartbeat messages to the cycler is automatically set to 2x this value, ensuring that we do not falsely trigger timeout errors.

For more in-depth information on the functionality of all APIs and their associated parameters, a user manual with all necessary information has been written and can be provided upon request from Unico or DMC.

End Result

With the creation of this driver set, Unico now has a tool that enables the full suite of their battery cycler’s capabilities to be seamlessly integrated into the workflow of battery labs and manufacturing lines across the country, especially those already utilizing DMC solutions.

One significant and relevant example of a DMC solution where this would apply would be our Battery Production Tester (Figure 3). DMC uses the same foundational Battery Test Platform modules to configure both validation (lab) and production (End-of-Line) test stations for our clients, meaning that Unico battery cyclers are now a logical option for customer consideration during the hardware scoping phase of DMC projects.

Learn more about DMC’s Battery Pack and BMS Test Systems. 

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The manufacturer approached DMC as soon as they identified the basic needs and challenges and chose us based on our demonstrated knowledge and experience testing similar products in the electrification sector.

DMC first took on a consulting role, leveraging decades of test engineering and technical expertise to collect and assess their requirements. Then, we collaboratively balanced the project tradeoffs (schedule, budget, risk, quality) against the technical performance of the new test system: resulting in a well-informed test specification and a conceptual test system design.

This collaborative ‘design phase’ quickly set up the entire project for success. The design phase uncovered several hidden requirements upfront, which resulted in faster convergence on the best test solution and allowed for continuous improvement with the flexibility to incorporate more complex quality assurance testing when they are needed.

The following ‘design/build/deploy phase’ used DMC’s standard ‘turn-key’ project process, resulting in the successful deployment of the client’s new automated test solution in their production facility within a few months.

Technical Details

The client’s product was designed to safely store hundreds of kilowatt-hours of energy in an internal battery system and provide that power to users in a variety of AC-power formats through several physical outlet options. It also featured a user-friendly touch-panel display for configuring the AC power output.

In their previous manual process, testing these units required operators with technical expertise, physical dexterity, and test instrumentation skills. The manual testing process involved taking numerous measurements to ensure they met specific manufacturing standards while repeatedly interacting with various knobs and switches in a predefined manner. It also involved the risk of manual probing into a high voltage receptacle.

Test System Architecture:

DMC physically assembled high-speed and high-precision instruments into a small-form-factor test rack, along with an industrial PC and peripherals, an AC power distribution unit, and a single main test signal distribution/breakout panel. The industrial PC acts as the single test controller and communicates with test instrumentation through a variety of communication busses (Ethernet, RS232, USB).

Test System Hardware:

Pickering High Voltage Multiplexer: Instead of requiring an operator connect and disconnect various parts of the test system with the high voltage connections of the device under test, a set of Pickering high-voltage, relay-based multiplexer cards were housed in an LXI chassis and used to automate the voltage switching functions. This allowed a custom software layer to manage all the switching connections.

Keysight DMM: Making accurate voltage and resistance measurements in quick succession meant using a robust DMM that could handle such usage. Selecting a benchtop-style instrument, connected over ethernet using the LXI standard, allowed DMC to strike a balance between performance and cost. As a bonus to having a highly-flexible DMM integrated into the system, DMC designed an automated self-test sequence: which used the DMM to verify the health and integrity of the test system itself.

NI-XNET Interface and NI cDAQ: To monitor for faults and unexpected behavior, the test system listened to the machine’s internal CAN bus using robust NI XNET hardware integrated into a cost-conscious NI cDAQ chassis and connected to the PC controller over ethernet.

Test SystemSoftware

NI TestStand: To allow the client’s test engineers to quickly modify test sequences, or develop new ones, we created custom test steps that allow drag-and-drop usage and rearrangement within the intuitive and powerful interface that TestStand provides. The built-in test report functionality of TestStand was also utilized to produce customized reports for every device tested.
 
Operator Interface: DMC’s leadership in the Test & Measurement industry comes with plenty of internal tooling, which saves development time and associated costs for customers. One of these tools is LabVIEW code that provides a simple user interface which connects to TestStand, presenting a simplified HMI experience for operators. The system allows for different types of products to be tested with different test sequences by simply scanning a barcode on the product prior to starting a test run.
 
Python Drivers: The DMC software team used the inter-operability features of TestStand to call Python hardware drivers. Python allowed the DMC team to easily integrate publicly available and instrument vendor provided packages, merge code, and review code from multiple developers. This freed up the team to focus on simplifying the end user experience with easy-to-use test steps that included signal multiplexing and instrument acquisition.

End Result

DMC’s system design effort automated nearly every step of the new testing process, reducing operator steps and limiting the client’s exposure to energized high-voltage connections. The test solution continuously monitors for issues, faults, and unexpected behavior within the product’s internal control system. A clean and simplified test interface allows operators to focus on quality, following clear, specific instructions to interact with the machine’s front panel, reducing the risk of errors, and significantly speeding up the testing process.

While the previous manual test system took 1.5 hours per unit tested, the new automated test system can complete a full product test in under 2 minutes. Every aspect of the test process, from checking the CAN bus for faults, probing every electrical outlet for proper voltage, or running load tests, is now fully traceable, accurately recorded, safer, and faster with the new DMC test solution.

Learn more about DMC’s Automated Test Stand Design services and contact us for your next project.

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The client provided DMC with a high-level description of their basic need for an incoming inspection on an aggressive timeline. DMC partnered with the client’s engineering staff to outline a high-level test specification. From this, we were able to quickly deliver a complete test system configured to the client’s specific needs. We met the client’s rapid start-of-production target by leveraging DMC’s battery test platform toolkit, National Instruments (NI) VeriStand, and the VeriStand Custom Device provided for Elektro-Automatik (EA) battery cyclers.

DMC engineers designed a solution based on the NI VeriStand platform and around COTS hardware from NI, EA, and other vendors. We designed the solution to perform the testing required for incoming inspection of the client’s battery packs.

We followed a well-structured, but highly accelerated, project process to design, program, fabricate, and commission the system. The completed system dramatically increased the client’s quality control capabilities relative to the manual inspections previously done.

DMC delivered a fully open solution (including all source code and hardware schematics), enabling the client’s in-house process and test engineers to maintain, refine, and expand the system over time — supporting any future test requirements. 

The DMC Battery Testing Advantage:

1. DMC collaborated with the client to develop firm test specifications from their initial high-level direction.
2. DMC developed a test system, hardware, and software with requirements based on test specifications, supported client reviews, and incorporated feedback into a final design approval.
3. DMC determined the best test system hardware and software to meet client requirements and be completed within aggressive schedule requirements.
4. DMC developed a high-level architecture for a long-term automated battery test system that met all test requirements and positioned the system for future flexibility and potential reuse/expansion.
5. DMC leveraged collections of internal template projects, pre-tested architectures, code libraries, and quality check processes to improve schedule and cost associated with software development — including the use of the NI VeriStand Platform.
6. DMC used a proven project process that involved quality checks, code reviews, and iterative testing to ensure project success.
7. DMC called upon several key “lessons-learned” from previous projects to improve the efficiency of onsite testing hours: improving schedule and cost.
8. DMC worked collaboratively with this client to provide full transparency and decision approval — while also acting as subject matter experts to recommend solutions, drive independent progress, and minimize the time investment required by client’s key engineering personnel.

Hardware Design and Architecture:

DMC worked with the customer to translate testing requirements into a concept system boundary diagram of the test stand. The diagram depicted the major hardware sub-systems, interfaces, and ownership. After incorporating client feedback and a final design review, DMC proceeded to detail out the client’s hardware system.

Test System Boundary Diagram

Based on the hardware requirements, DMC selected an EA PSB-model bi-directional power supply (also known as a battery cycler or inverter) to interface with the high-voltage connection of the client battery pack. Engineers used this  battery cycler to charge and discharge the battery pack under the system PC’s control. DMC has partnered with EA and NI on many projects involving battery simulation and testing, so our engineers had full confidence in the NI and EA provided LabVIEW software drivers and VeriStand Custom Device Module. These were key pieces to the test station performance as well as the rapid software development process.

EA PSB Series Battery Cycler for charge/discharge

The test system used a custom-designed electrical sub-system to interface with the battery pack low-voltage power supply lines. It used CAN communication busses to control and monitor the pack during test activity. This subsystem utilized the NI cDAQ platform for integrating the digital I/O and CAN communications interfaces with the PC controller.

Custom Electronic Sub-System for Battery Pack Control and Communications (Top, front. Bottom, back.)

Design for Electronic Sub-System Enclosure

Software Architecture:

To increase the speed of the software development effort while meeting all system requirements, DMC selected the NI VeriStand development environment to serve as the framework of the software control system. VeriStand allowed DMC to take a platform-based approach that emphasized configurability and ease of use, while also allowing quick customization of test profiles so that they fit the client’s immediate needs exactly.

The NI VeriStand platform is used extensively throughout a broad range of industries to provide a powerful “data engine” foundation upon which purpose-built automated test systems can be established. VeriStand is easy to set up and use, and it has many powerful features that provide a fully comprehensive test system.

VeriStand project used for this solution

While the VeriStand data engine is typically run on NI real-time targets, such as CompactRIO or PXI controllers, this test system took advantage of VeriStand’s capability of running on a standard Windows PC. When running on a real-time target, the target’s operating system ensures that the timing of tasks is guaranteed within a very tight tolerance. Since this application did not require the strict timing of a real-time system, we used PC-based timing to acquire data and execute calculations at sufficiently regular and reliable intervals.

While VeriStand does not require programming skills for basic systems design and use, it does allow developers to leverage full Application Programming Interfaces (APIs) to extend and customize the system. Custom devices can be built using LabVIEW and can then be seamlessly integrated into VeriStand’s engine.  For this specific project, DMC used the EA Battery Cycler custom device plug-in to provide quick, easy, and full control of the EA cycler from within VeriStand.

VeriStand model developed for this test solution

VeriStand was also used to monitor the hundreds of CAN channels being broadcast by the battery pack BMS during the test. Adding these channels to VeriStand involved simply importing the CAN database file the client provided and selecting the channels to monitor along the EA cycler channels.

This test system took full advantage of VeriStand’s flexible and native alarming system, which allows users to fully monitor critical battery system and cycler channels based on predefined constants or variables. This dynamic alarming notified the operator of the system state that triggered the alarm, and they took action quickly to shut down the system to a safe state.

VeriStand ships with a sequence editor that allows you to start sequences: which can edit variables, handle looping logic, and operate on multiple tasks at once. These simple, but powerful, sequences were used to provide the main test logic of the application and to interact with the system hardware components.

VeriStand Test Sequences for Battery Pack Testing

VeriStand executes its main control loop independently of the user interface (UI).  This means a UI can be edited on the fly while tests are running, but it can also be locked to prevent accidentally making modifications to a standard UI. An indicator for a particular channel (including a graph or chart) can be added to the UI anywhere it is needed.

VeriStand Operator Screen

VeriStand alarm details screen

VeriStand allows users to easily implement a variety of data logging types and destinations within a test system. For this solution, DMC configured detailed logging of system operational state, detailed CAN bus logs, and internal variable changes to a timestamped TDMS file whenever the system is running a battery test sequence. This feature allows the user to quickly and easily debug and troubleshoot any failed test runs.

Project Outcome:

DMC delivered this automated battery pack test system to the client’s new manufacturing facility — meeting their aggressive timeline and test requirements. This DMC system has consistently ensured the quality and safety of every pack integrated into the electric drivetrain of their new battery-powered commercial electric vehicles.

Click Here for more information on DMCs latest generation of Battery Production Test systems.

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For this project, DMC automated the client’s previously manual testing process. This increased efficiency while maintaining quality, as automated testing is faster and less error-prone. With our extensive experience in automated battery testing, we were qualified to follow the client’s step-by-step process and create a tester tailored to their needs.

Functional Specification

The test stand comprises a high-performing NI 4065 Digital Multi Meter (DMM), an NI RMX-4101 programmable power supply, and a Hioki ST5520 Hipot meter for measurement instrumentation. This test suite makes a wide range of testing options available to the client. A Pickering Switch Matrix and a Pickering High Voltage Multiplexer provide a robust switching infrastructure to allow additional instrumentation to be added or new test configurations to be defined depending on future product requirements.

Switch Matrix

The core of the test system is built around a Pickering switch matrix which allows many connections between Device Under Test (DUT) signal lines and instrumentation. This is the heart of the test system’s ability to adapt to changing product requirements.

Not only does the switch matrix allow the test stand to reconfigure a test setup in real-time, it also allows for the addition of instrumentation or DUT signals in the future with minimal changes to hardware or software.

Digital Multi Meter (DMM)

The DMM, in combination with the Pickering switch matrix, allows the test stand to make differential voltage measurements between any two DUT signals or single-ended measurements referenced to ground or the common line of the programmable power supply.

Programmable Power Supply

The PDU provided the power to the Battery Management System (BMS). The Programmable Power Supply (PPS) allows the test stand to apply a wide range of voltages or voltage profiles to the DUT, allowing the PDU to be tested under a wide variety of operating conditions.

The Hipot meter allows the test stand to perform Hipot testing on the DUT. In this case, the Hipot meter was combined with the Pickering high power 12 bank 2:1 multiplexer to provide high voltage isolation for up to 12 DUT lines.

Stand Form

All of this measurement and switching hardware is contained in a compact rollable test cart. This test cart provides the operator interface along with the interface for the DUT.

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