an approach to robust, no surprises design verification testing [presentation slides]

TÜV SÜD 03/05/23 Battery Safety 2012 Slide 1

A New Approach to Robust, No Surprises Design Verification Testing

Erik J. SpekChief EngineerTϋV SϋD Canada

Battery Safety 2012


The end user of battery driven cars expect the same if not better than conventional cars.

Is this possible?

Do the normal engineering tools work?

Battery Safety 2012


Background Note:

The material for this presentation comes from experience with many programs to develop and launch automotive products both in the traditional automotive products and battery operated vehicles including 12 volt safety components and the Ford/ABB Ecostar

Battery Safety 2012


Discussion Areas:

1.Background2.The normal DVP (Design Verification Plan)3.The differences between normal cars and electrically driven cars4.How do the risks of battery systems influence the DVP5.Some ways to address the differences and examples

Battery Safety 2012


The acid test of how well a product meets customer expectations.

Confidence ???

“Consumer Reports review details flaws in Fisker Karma sports car”

“Tesla Motors’ Devastating Design Problem”

“Nissan Electric Cars May Lose Range In Hot Climates”

What gives us confidence in the product?

“Probe of GM's Volt Fires May Be Lengthy”


If the product fails, as the design engineer you will receive plenty of attention

$$$

The Attention You Don’t Want


• The vehicles we buy, drive and maintain today are considered to be:

• predictable, • reliable, • robust against abuse• and afford the occupants a

measure of survivability in accidents.

• Automotive product development process:

• proven method to ensure end product meets customer wants and needs.

Expectations


• Design Verification Plan (DVP) with a variety of tests:

• Shake and drop• Hot and cold• Altitude• Water showers and immersion• Corrosion• Fire exposure• Impacts• Humidity• Controls• 12 volt source• etc

Verification of Expectations


• DVP uses the best available information on abuses that can be imposed.

• Not a guarantee of no risk• Unforeseen abuse conditions may occur in 12v

components leading to loss of function• Aged components• Humidity and dust • Abnormal uses• Salty air• Example: major recall on Chrysler minivan

sliding door cable abrasion & short circuit

Guaranteed Verification ???


• DVP may take multiple passes-usually do!• Methods and equipment are well established• Costs are known and managed• Timelines are weeks to months after parts made• Product level is usually ‘cut and weld’• Program managers are trained to ‘make it

happen’ ON TIME and ON BUDGET through:• Extraordinary measures as needed• War room approach• More budget if needed

• VEHICLE LAUNCHES MUST HAPPEN ON TIME

Consequences of Failed DVP


• High voltage – hundreds of volts• Dangerous power levels• High level of stored energy – for

extended power delivery• Common implied expectation is

‘batteries not as hazardous as gasoline’

• Even 12 volt batteries can burn• An invitation to product liability lawyers

• Noxious fumes• Electric shock• Survivable vs unsurvivable accidents• Product liability

Are Electric Vehicle Batteries Different?


• 4 levels of product involved:• individual cells, • 10s of cells in modules, • 10s of modules in a pack, • pack in a vehicle

• Each level contributes to overall robustness verified by DVP tests• The final product (pack) is the last line of defense against abuse.• Pack subjected to variety of tests:

• Mechanical• Electrical• Thermal

• Each level has risks NOT NORMALLY FOUND IN USUAL AUTOMOTIVE PARTS

How Does This Affect The DVP?


• The aim of the DVP is:• Successful outcome of tests• No damage or injury to people, equipment and facility• NO SURPRISES

• DVP is hard enough and costly without surprises• What surprises can occur:

• Accidents in testing• Known defects in product heading into testing compromising

outcome• Incorrect design level of component• Unpredictable outcome

• SHOW STOPPERS …. Slows or stops the program

DVP Surprises


Everything is great until an electric car is in an accident or fire ……………… then:

Product Liability Lawyers circling looking for:• Incomplete documentation• Holes in the DVP test plan• Stranded tests – exposed risks• Evidence of haphazard approach• Unnecessary and or misleading data• Accidents during testing• Uncontrolled approach• Lack of engineering discipline

Risk of getting it wrong


• Batteries including cells and modules are always on – inside• Laws of physics and chemistry are always present• Mechanical parts will break• Liquids will leak• Current carrying parts will overheat• Plastic parts will become hot and soften• Tests will cause failures• Incorrect parts will be made and used

The Unavoidable


• Accepted risks for any 3rd party test house or inside test lab

• Electric shock:• Current path to touchable surfaces• Can happen at any time during testing or

use• Hundreds of volts (safe handling level is <

60Vdc)• Dangerous gases and fumes (HF, soot, etc• Fire• Explosion• Combinations of different tests introduce

compound hazards • Shake and bake and cycle

Know the Risks


• DVP is not an R&D exercise or taking unnecessary risks• DVP should report confirmation of a successful verification test

• If the outcome of the test is in doubt or has not been tried:• Do the R&D work first as EXPLORATORY

• Stage the work:• Simplest level first –controlled and unpowered• Apply power from a controlled source• Repeat with battery cells installed

Exploratory vs Confirmatory Testing


• Abuse tests may not show latent defects unless careful post test analyses are conducted

• Semi-broken or fatigued bus high voltage components • Effect of a lifetime of dust, humidity leading to isolation

degradation in ohmic value• Increased hazard from aged cells

• Unsurvivable accident: clear catastrophic result• Survivable accident: occupants pinned waiting for extraction only to

be hurt by a battery hazard• Subject to possible product liability action

Survivable vs Unsurvivable Accidents


• Some vessels can tolerate a bit of salty water on board

• Keeping the ship afloat can be achieved by bailing and bilge pumps

• Ship electrical bus systems can tolerate the presence of conductive water

•BATTERIES ARE DIFFERENT-NO WATER ALLOWED!!!!!

Example: Water Immersion


• Test: immerse pack in 5% salt water solution or salt fog – some call fro hot pack into ice cold water

• Objective: determine consequence if water leaks into pack

• Consequence: conductive water in high voltage pack:

• Uncontrolled dissociation• Cl2 and H2 – both dangerous

• Pack leaks= high risk & SURPRISE• Solution: verify pack leak worthiness• Staged approach:

• 1-EXPLORATORY: No cells• 2-EXPLORATORY: Cycler powering high

voltage bus• 3-CONFIRMATORY: complete pack test

Example: Water Immersion


• Test: vibrate packs and shock to known profiles• Objective: primarily verify no parts become loose, fatigued or broken • Consequence on failure:

• High voltage bus compromised immediately or later• Pack leaks= high risk & SURPRISE• Solution: verify pack hardware structural integrity• Staged approach:

• 1-EXPLORATORY: dummy cells• 2-EXPLORATORY: cycler powering high voltage bus• 3-CONFIRMATORY: complete pack test

Example: Vibration & Shock


• Plug In Hybrid Electric Vehicles (PHEV) carry gasoline on board• Substantial batteries also on board• A fuel fire is a possible event• Test: subject pack to fuel fire • Objective: verify response to external fire• Consequence of failure:

• Aggravated risk of fire or explosion• Solution: verify pack fire resistance• Staged approach:

• 1-EXPLORATORY: dummy cells• 2-EXPLORATORY: pack with active module• 3-CONFIRMATORY: complete pack test

Example: Fire Resistance

TÜV SÜD

Appropriate Facilities

03/05/23 Slide 23

Be Able to Contain Reactions up to Explosions (EUCAR 7)

TÜV SÜD

Closing

03/05/23 Slide 24

DVPs for Battery Operating Cars:

1.Show only confirmation of tests for records

2.Keep exploratory tests as pre-DVP

3.Ensure that the tests in the DVP encompass all

reasonable abuse that could be encountered

4.Use a staged approach in R&D stage to build

success in hazardous tests

TÜV SÜD 03/05/23 Slide 25

Thank You !

an approach to robust, no surprises design verification testing [presentation slides]

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