97©2012 IEEE Electromagnetic Compatibility Magazine – Volume 1 – Quarter 1

Automotive EMC Testing – The Challenges of Testing Battery Systems for Electric and Hybrid Vehicles1

Defining the Test Methodology using System Engineering

This paper is adapted by Terry M. North of Jastech EMC Consulting, LLC from a presentation by

James Muccioli of Jastech EMC Consulting, LLC at the 2011 IEEE EMC Symposium Transportation Systems

EMC workshop. The presentation was coauthored by Dale Sanders of Jastech EMC Consulting, LLC.

Abstract – Hybrid and electric vehicle batteries are actually an Energy Storage System whose internal module functions include: battery monitoring and control, DC to DC convertor(s), an internal battery charger and internal battery cooling control. As a result, comprehensive EMC testing requires a paradigm shift from module or component level testing to complete EMC system level testing.

Introduction

The focus of this presentation is to share the challenges and flexi-bility that a test facility needs to address in order to accommodate OEM approved Test Plans and development testing.

The density of packaging and complexity of hybrid and electric vehicle battery systems is readily apparent in the following photos.

What is New to EMC Testing?

We are not just testing a battery module, but an Energy Storage System.

The paradigm shift is moving to complete EMC system level test-ing from module or component level testing.

The Energy Storage System can be designed with the following modules: 1. Battery control module2. DC to DC convertor module3. Internal battery charger4. Internal battery cooling module5. Other modules

¹ Adapted from the presentation of the same name included in the workshops/tutorials of the 2011 IEEE International Symposium on Electromagnetic Compatibility.

98 ©2012 IEEE Electromagnetic Compatibility Magazine – Volume 1 – Quarter 1

Writing an EMC Test Plan

The person writing an EMC Test Plan must understand three things about the Device Under Test (DUT) or System Under Test (SUT).1. What EMC standards should the SUT be tested to and how do

they apply to the test setup?2. What are the operating states of the SUT to be tested?3. What are the conditions when an RF field is applied or mea-

sured that determines a pass or failure criteria for the SUT?

Systems Engineering Approach to EMC

Before discussing the process for developing good requirements, some important definitions must be established:

System: a set of components acting together to achieve a set of common objectives via the accomplishment of a set of tasks.

System Behavior: a sequence of functions or tasks, with inputs and outputs that must be performed to achieve a specific objective.

Requirement: mandates that something must be accomplished, transformed, produced, or provided. The attributes of a good requirement are that it is unambiguous, understandable, traceable, correct, concise, unique and verifiable.

Traceable: in reference to requirements; a requirement is said to be traceable if one can identify its source. The source may be a higher level requirement or a source document defining its existence. An example would be if a component level require-ment (weight, reliability) is traceable back to a vehicle level requirement.

Operational Concept: an operational concept is a shared vision from the perspective of the users and development participants of how the system will be developed, produced, deployed, trained, operated, maintained, refined and retired to meet the operational needs and objectives.

Step 2-3 - Identify, Discover and Understand Requirements

Identify Source of Requirements:• North American, Asian and European Module EMC standards• Military standards

Discover and Understand Requirements:• Radiated RF Emissions• Conducted RF Emissions• RF Immunity• Magnetic Field Immunity• Power Cycling and Transient Immunity• Electrostatic Discharge

99©2012 IEEE Electromagnetic Compatibility Magazine – Volume 1 – Quarter 1

How do these requirements change for an Energy Storage System?

Things to Consider in Testing a System

If the vehicle supplies the loads, charging and regenerative charg-ing from braking to the Energy Storage System: • What would be required to mimic the vehicle interactions when

testing the system?• How would this system level testing affect the test time required

when running through the different modes of operation?• Are there additional modes or longer dwell times required to

adequately assess the system response?• If the testing is not done at the system level first, what will be the

impact to the number of vehicles required for verification (not validation) at the vehicle level?

Note: Validation is confirming that a product or service meets the requirements.

Verification is the process for quantifying and accepting the requirements.

Things that Must be Addressed in the Test Plan

Due to the size, weight and complexity of the Energy Storage Sys-tem, the following items need to be addressed with the test lab and documented in the test plan:

• Considering the size and weight of a typical hybrid or electric battery system, how will this be handled in the immunity and emission tests?

• Will the test lab have the capability for increased monitoring of the various modules in the system during testing?

• What additional equipment is needed to simulate sensors, loads, data bus, etc. of the vehicle operation of the System Under Test?

Radiated RF Emissions and Immunity

Another thing to consider in performing a radiated emissions or immunity test is how to place and activate the high and low voltage wiring harnesses for the Energy Storage System.

Some options:• Testing the low voltage wiring harness with no power to the high

voltage harness.• Testing the high voltage wiring harness with no power to the low

voltage harness.• Testing with power to both high and low voltage wiring

harnesses.• Testing with power to both high and low voltage wiring harness-

es, but shield the high voltage wiring harness.• Other possible modes.

100 ©2012 IEEE Electromagnetic Compatibility Magazine – Volume 1 – Quarter 1

Magnetic Field Immunity

When writing a test plan for an Energy Storage System, one must consider how the magnetic fields will affect the system.

Below are some items which should be addressed:1. Which sensors are likely to be affected by the magnetic fields?2. How will this affect the way the system reacts working normally?3. Should the system have the high voltage and high current lines

activated during testing to see if these added fields affect the switching contactors opening and closing?

4. How will any plastic or metal enclosures affect the paths for the magnetic fields?

5. How the high current lines are routed in the Energy Storage System near the magnetic field sensors and is this representa-tive of production intent?

Power Cycling and Transient Immunity

When testing the Energy Storage System for transient immunity and power cycling, one of the most important things to consider is how to monitor the system and what standards apply.

Below are a few items which need to be addressed in the test plan:1. The diagnostic bus can be used to monitor the multiple interfac-

es to the different modules in the system, provided that the soft-ware will capture the anomalies.

2. Will the sensors be affected by the transients and give bad data to the system?

3. Define a way to monitor the contactors on the high voltage side to tell if they are truly open or closed.

4. Define where a DVM must be used to measure the voltage and current at different places in the system before and after the test

Electrostatic Discharge Bench Test1. Since there are multiple modules in the Energy Storage System,

where should the ESD test points be located?2. How should the test plan be specified using the resistive mat

and bleed off resistor?3. Should the sheet metal of the vehicle body be part of the bench

testing?

BiographyTerry M. North received both BSEE and MSEE degrees from Wayne State University. His early experience includes service with the U. S. Army in RF communications and with Ford Motor Company in advanced fuel systems design. Joining Chrysler in 1985, Mr. North was one of the early contributors in the effort to develop an EMC analysis and testing

capability with an automotive focus. Over the more than 20 years that he was with Chrysler, he contributed to the development of a world class in house automotive EMC capability, which assisted in the advancement of the automotive industry in EMC. Mr. North was also involved in the EMC development and qualification of passive restraints systems at Chrysler. He was a major contributor in the development of Chrysler corporate EMC standards and served as a consultant on EMC and E/E systems issues. As a Senior Engineering Specialist with DaimlerChrysler, he also contributed to the development of international EMC standards that com-bined different backgrounds and processes. He is a member of the SAE EMC Committee and its Integrated Circuits EMC Task Force and is the co-author of the SAE J1752 series of standards. Mr. North has three patents for EMC test development and has co-written several papers on IC RF Emissions and EMC test development that were presented at IEEE Sym-posiums. Mr. North has more than 20 years of experience in EMC and is a senior member of the IEEE. After his retirement from Chrysler, Mr. North joined Jastech EMC Consulting, LLC. Recent projects include EMC stan-dards and test support for Cooper Standard Automotive. He may be reached at tmnorth@ieee.org.