Case Studies

Battery Control Unit Tester for Remanufacturing and Warranty Servicing Process

Posted in Automotive, Battery Pack Test Systems, Energy and Utilities, Green Technology, LabVIEW, Test & Measurement Automation, Test and Measurement, Test Stand

Summary

DMC utilized the DMC Battery Test Platform to develop a Test Control Panel software application to perform automated testing of the Battery Control Unit (BCU) for a Client's automotive lithium ion battery pack.

This test system allowed the Client to instate an efficient process for evaluating the operating state of the Battery Control Units in battery packs returned under warranty claims, and thereby greatly reduced the cost of servicing these warranty claims.

Battery Control Unit Test Stand

Battery Control Unit Tester

Solution

Experienced Client engineers selected the instrumentation/components, designed the hardware platform for the battery module test station, and developed test specifications to define the desired testing procedures.  Although the Client had expert test engineering and software programming resources on staff, the Client chose to engage DMC to handle the software programming portion of the test system development.  This allowed the Client to expedite the overall implementation schedule of the test system (in turn allowing the Client to begin realizing cost savings sooner from reduced warranty servicing costs), as well as to allow the Client's engineering resources to focus their valuable time on developing and executing their battery pack remanufacturing process.

DMC programmed a LabVIEW-based Test Control Application to test the Battery Control Unit in full accordance with the Client's prescribed testing specifications.  DMC implemented this application rapidly by leveraging existing code modules from the DMC Battery Test Platform and molding these preexisting frameworks to the Client's unique hardware architecture and testing requirements.  

The Test Control Application provides fully automated functional testing of battery pack samples through a "Test Executive" architecture.  This highly configurable architecture allows engineering users to establish a library of defined test procedures by adjusting input settings and grading criteria for pre-defined test processes (based on testing specs).  A flexible test sequence management interface then allows these test procedures to be sequenced together to build a comprehensive functional testing regiment.

The Test Control Application also provides users with a Manual Mode interface that provides direct, on demand control of all test stand connections and instrumentation.  This increases the overall flexibility of the test system by allowing operators to perform ad-hoc testing operations and detailed diagnostic investigations that are not formally instantiated as part of an automated test procedure.

The automated testing capabilities provided by this test station include the following:

  • DUT Connection Test: Performs appropriate continuity measurements to ensure proper Device Under Test connection to test stand
  • 2 Point Resistance Measurement Test: Performs resistance measurements between pairs of DUT connection points to verify proper impedances and continuity/connection paths
  • CAN Response and Programming Test:  Verifies CAN and CCP communications with the DUT are operating properly and obtains DUT model and software version information of current DUT
  • Isolation Resistance Test:  Performs DC HiPot isolation resistance measurements between configurable DUT Connection points (e.g. from Battery Control Unit's high voltage bus to low voltage / chassis connections)
  • Voltage Sense Test: Verifies that the Battery Control unit is properly and accurately measuring and reporting full stack voltages and cell voltages across a range of expected pack voltages
  • Thermistor Sense Test:  Applies configurable resistances to the DUT's Thermistor sense connections, and verifies that the Battery Control Unit is properly and accurately measuring and reporting thermistor temperature data and associated temperature based fault codes
  • Current Sensor Test:  Applies a configurable current flow through the DUT's current sensor to verify that the Battery Control Unit is properly and accurately measuring and reporting current flow (in both directions)
  • Isolation Detection Test:  Induces an isolation fault between high voltage and low voltage / chassis connection points on the DUT and verifies that the DUT properly identifies and responds to this fault condition

Customer Benefits

Previously, the Client had no manageable process for evaluating battery packs that were returned by the Client's customers during the warranty period to identify what, if any, faults were actually present in the returned packs.

The test stand programmed by DMC allowed the Client to implement an efficient process to identify and isolate root causes of faults or performance issues within the Battery Control Unit of these returned battery packs.  The Client obtained a large ROI on the implementation of this test system from a major reduction in the overall cost of servicing warranty claims, and provided their customers with the option of replacing damaged out-of-warranty battery packs with a low cost, high quality remanufactured component.

Instead of being saddled with the high costs of providing customers a new replacement pack with "no questions asked", the Client was able to manage warranty claims in an optimal manner for each returned battery pack.  The Client was able to perform targeted repairs for fault cases which involved issues isolated to the Battery Control Unit, directly replace the small subset of packs with prohibitive repair costs, and redeploy returned packs that in fact had no faults and were perfectly operational.

Technologies

  • LabVIEW Development Environment
  • NI USB CompactDAQ
    • NI 9477 Sinking Digital Output C Series Module for digital control of system contactors and relays
    • NI 9221 8 Channel Analog Input C Series Module for Analog Input measurements of output from temperature and humidity probes, and feedback on system safety interlock state
    • NI 9862 1-Port High-Speed NI-XNET CAN C Series Module for CAN and CCP (CAN Calibration Protocol) with Device Under Test
  • Lambda-TDK ZUP Low Voltage Low Current DC Power Supply for powering BCU and contactors
  • Agilent Model N5772A High Voltage DC Power Supply for powering a cell voltage simulator module to apply cell voltages and battery stack voltages to BCU for simulating battery stack current flow through the BCU current sensor
  • Agilent Model 34410A Digital Multimeter for measurement of DUT resistances and voltages
  • Hioki 3154 HiPot Meter for Insulation Resistance Testing between high voltage and low voltage/chassis connections