UN 38.3 Lithium-ion Battery Testing

Vibration and Shock Testing Requirements

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UN 38.3 Lithium-ion Battery TestingTopics

• Key points of presentation• UN 38.3 test overview• UN 38.3 vibration and shock test details• Mild and full hybrid electrical vehicle battery systems• Vibration and shock issues• Vibration test analysis and recommended change• Shock test analysis and recommended change• Summary• Back-up

– Transportation scenarios– Calculations– Vibration Isolation– Aviation shock specification

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UN 38.3 Lithium-ion Battery Testing RequirementsKEY POINTS

• Lithium-ion batteries designed for hybrid electric vehicles (HEV) are large and complicated structures.

• Lithium-ion HEV batteries are proven to be durable and safe for vehicle usage by extensive testing.

• Applying the existing vibration and shock requirements to lithium-ion batteries designed for use in HEVs will increase the cost of HEVs and delay the adoption of HEVs in the market.

• Existing vibration and shock requirements are not valid for heavier lithium-ion HEV batteries.

• The existing requirements can be modified for large batteries and still assure safe transportation.

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UN T1-T8 TestsUN 38.3 Manual Of Tests

• T1 – Altitude Simulation• T2 – Thermal Shock• T3 – Vibration • T4 – Physical Shock

• T5 – External Short Circuit• T6 – Impact • T7 – Overcharge • T8 – Forced Discharge

• Tests were designed primarily for cell phone and laptop cells and batteries.

• Tests simulate shipping environment and conditions, not the usage environment

• All tests must be passed

• Tests are without packaging

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UN 38.3 Manual Of Tests T3 Vibration Testing Requirements

• 16 batteries– 8 Fully charged

» 4 fresh and 4 with 50 cycles usage– 8 Discharged

» 4 fresh and 4 with 50 cycles usage

• 3 hrs in each of 3 mutually perpendicular mounting positions• Logarithmic sweep from 7Hz to 200Hz to 7Hz in 15 minutes

– 7Hz to 18Hz at 1gn; amplitude decreasing

– 18Hz to ~50Hz with 0.8mm amplitude; acceleration increasing to 8gn

– ~50Hz to 200Hz at 8gn; amplitude decreasing

– 200Hz to ~50Hz at 8gn; amplitude increasing

– ~50Hz to 18Hz with 0.8mm amplitude: acceleration decreasing to 1gn

– 18Hz to 7Hz at 1gn; amplitude increasing

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UN 38.3 Manual Of Tests Current T4 Shock Testing Requirements

• 16 batteries– 8 Fully charged

» 4 fresh and 4 with 50 cycles usage– 8 Discharged

» 4 fresh and 4 with 50 cycles usage

• 18 shocks: 3 in negative and positive direction of 3 mutually perpendicular mounting positions

• Shock parameters– Normal batteries: Half-sine, 150 gn peak acceleration, 0.006 seconds pulse

duration– Large batteries: Half-sine, 50 gn peak acceleration, 0.011 seconds pulse

duration– Note: Large batteries have more than 500 grams ELC

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UN 38.3 Manual Of Tests Pass Criteria for Both Tests

• No mass loss• No leakage or venting• No disassembly• No rupture • No fire• OCV after test > 90% of OCV before test

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HEV Lithium-Ion BatteriesMild and Full Hybrid Applications

• Mild Hybrid Applications– One electric motor– Vehicle Functions

» Assist during launch and acceleration» Stop/start engine when vehicle stops» Regen braking

– 120 volts (32-36 cells)– Less than 500Wh– 14 kg battery assembly

400 x 250 x 150 mm

16 x 10 x 6 inches

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HEV Lithium-Ion BatteriesMild and Full Hybrid Applications

• Full Hybrid Applications– Multiple electric motors– Vehicle Function

» Allows electric only propulsion» Stop/start engine when vehicle stops» Regen braking

– 300-320 volts (approx. 80-88 cells)– Less than 2000Wh– 45-50 kg battery

1000 x 350 x 300mm

40 x 14 x 12 inches

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HEV Lithium-Ion BatteriesTypical Usage, Vibration and Shock OEM Vehicle Requirements

• Useful Life: 15 years/ 150,000 miles

• Vibration Test Requirements– Random vibration– 1.28 grms – 10 to 2000 Hz– 24 hours/axis

• Shock Test Requirements– Mild HEV Battery Assembly

» 132 shocks/axis at 25g’s, half-sine, 15 ms» 6 shocks/axis at 100g’s, 11 ms

– Mild and Full HEV Package» 10 shocks/axis at 50g’s, 6 ms

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HEV Lithium-ion Battery Transportation

• Prototype or Development Stage– Air and vehicle modes utilized but mostly vehicle– Domestic and international– Multiple shipments possible for the same battery (some in the vehicle)– Batteries have not passed UN 38.3 testing– Competent Authority will be used to allow shipping

• Production– Vessel and vehicle modes normally– Domestic and international– 5 or less shipments of battery before vehicle installation– Starts in 2010– Must pass UN 38.3 tests or obtain special approval

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UN 38.3 Vibration and Shock TestingIssues and Impact

• Per Delphi Analysis and Experience:– Current battery pack designs for mild and full hybrid applications are

expected to fail the T4 vibration test– They may also fail the T3 shock test

• Redesigning to pass UN vibration and shock tests would add development time, mass and cost to HEV battery systems :– That have already met requirements for 15 years of vehicle usage– That will be shipped only a limited number of times and rarely be air

• Impact– HEVs will be more costly to the consumer and possibly delayed – Adoption of HEVs will be delayed along with their ecological and energy

benefits

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UN 38.3 Vibration and Shock TestingTest Analysis

• Mild hybrid lithium-ion battery packs are about 14kg gross. – Maximum T3 vibration force will be ~27,000N.– T4 shock will be ~41,000N.

• Full hybrid lithium-ion packs are about 48kg gross. It is not a large battery by current definitions.– Maximum T3 vibration force will be ~94,000N.– T4 shock will be ~141,000N.

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Vibration Test Analysis

• HEV battery systems are assemblies of electronic controllers, sensors, air flow ducts, cabling, cell mounting fixtures, cells, trays, covers and attachment brackets.– They are not “solid” like cells and laptop batteries.– They will have several resonant frequencies under 200 Hz.– Estimated force exerted on mild HEV batteries due to damping and

resonance is approximately 27,000N.– Full HEV battery force is approximately 94,000N.

• With the understanding that vibration test parameters are based on air transportation of small lithium cells and batteries, these parameters do not realistically apply to larger batteries.

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Vibration Test Analysis

• UN T3 testing of HEV batteries at these frequencies and 8gn is unreasonable because:– Vibration of the transportation mode is reduced due to the mass of the pack.– Test requires vibration to be “faithfully” transmitted to device, yet vibration

would not directly pass from the transportation mode to the battery due to the isolation provided by the skid or container and the package.

– Force levels can not be transmitted by the transportation mode » Force required to vibrate a large notebook computer battery (0.5 kg) is

~1000N.» 27,000N and 94,000N are very substantial forces

• 2750kg wrecking ball falling• Or stopping a 550kg wrecking ball after falling 1 second (35kph/22mph) in 1 meter • 9500kg wrecking ball falling• Or stopping a 550kg wrecking ball after falling 1 second in 0.28 meters

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Vibration Test Analysis and Recommendation

• T3 Test Recommendation For batteries > 12kg:– Reduce force level from 8gn to 2gn

• Basis for recommendation– Force levels are more realistic and exceed current exerted forces.

» Force required to vibrate cell and notebook batteries at 8gn~1000N» 1000N applied to vibrate a mild hybrid battery is ~0.33g.

– 2gn is equivalent to 5880N for a 12kg pack

– 9 hours of swept-sine vibration testing at 2gn is still a severe test for a large battery.

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Shock Test Analysis and Recommendation

• T4 shock forces on mild HEV batteries would exceed 40,000N. – Full HEV battery forces would be >140,000N.

• Again, with the understanding that these shock values are based on air transportation of small lithium cells and batteries, these parameters do not realistically apply to larger batteries.

• UN T4 testing of HEV battery packs at these forces is unreasonable because:

– These force levels could not be transmitted by the transportation mode » Force required to shock cell phone and notebook batteries at 150gn~1500N» 1500N applied to shock a mild HEV battery (~500Wh, 12Kg) is ~6.5gn.

– There is no source for the additional 38,000N.– Aviation specifications (RTCA) test for Crash Shock at 20g maximum.

• Recommend limiting acceleration to 50gn for all batteries > 12 kg– Far exceeds realistic and expected levels– 50gn already is used in UN 38.3 for large batteries.

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Summary

• Mild and full HEVs will have lithium-ion batteries that will have to be tested according to UN 38.3 Manual of Tests

• UN 38.3 T3 vibration and T4 shock tests are unrealistic when applied to large batteries

• If these tests remain as currently written, conversion of the world vehicle fleet to hybrids will be delayed

• Proposed T3 modification is to reduce g level from 8 to 2 for batteries 12kg or heavier

• Proposed T4 modification is to reduce g level from 150 to 50 for batteries 12kg or heavier

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Back-up Material Follows

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Back-upHEV Lithium-ion Battery Transportation Scenarios

• Prototype or Development Stage1. Battery transported from manufacturer to airport by vehicle2. Airport to airport3. Airport to distribution center by vehicle4. Distribution center to HEV system integrator by vehicle5. HEV system from system integrator to OEM engineering by vehicle6. HEV (car) from OEM engineering to test site by vehicle7. HEV (car) back from test site to OEM engineering by vehicle8. HEV system from OEM engineering back to integrator by vehicle

• Production Stage1. Battery transported from manufacturer to marine port by vehicle2. Marine port to marine port3. Marine port to distribution center by vehicle4. Distribution center to HEV system integrator by vehicle5. HEV system from system integrator to OEM assembly plant by vehicle

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Back-upCalculations

• Resonant Vibration Force at 8gn – Force = [mass] x [acceleration]/[ξ, the damping constant] – Damping constant is set at .04, empirical value based on testing similar

designs– Mild Hybrid Force = 14x8x9.8/(.04) N or ~27,000N.– Full Hybrid Force = 48x8x9.8/(.04) N or ~94,000N.

• Shock Force at 150gn

– Force = [mass] x [acceleration] x Dynamic Amplification Factor – Dynamic Amplification Factor is set at 2– Mild Hybrid Force = 14x150x9.8x2N or ~41,000N.– Full Hybrid Force = 48x150x9.8x2N or ~141,000N.

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Back-upVibration Isolation

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●

Mass of Pack Mass of Pack

K Stiffness of battery K Stiffness of battery

Kp Stiffness of packaging

Kc Stiffness of container

In testing, vibration is transmitted to the battery depending on the stiffness of the battery.

Ktest = Kbattery

In reality, vibration is transmitted depending upon the stiffness of the container, the packaging and the battery.

Kequivalent = 1 1 + 1 + 1 Kbattery Kpackaging Kcontainer

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Back-upCalculations

• Stopping a wrecking ball examples: – 550kg wrecking ball after falling 1sec in 1 meter– Forceavg x distance = mass x velocity2/2– Forceavg = (mass x velocity2 ) / (2 x distance)– Forceavg = 550kg x (9.8m/s)2 / (2 x 1m)– Forceavg = 26411 kgm/s2

– Forceavg = 26411N

– 550kg wrecking ball after falling 1sec in 0.28 meters– Forceavg x distance = mass x velocity2/2– Forceavg = (mass x velocity2 ) / (2 x distance)– Forceavg = 550kg x (9.8m/s)2 / (2 x 0.28m)– Forceavg = 94325 kgm/s2

– Forceavg = 94325N

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Back-upCalculations

• Vibration force required for a large notebook computer – Force = [mass] x [acceleration]/[ξ, the damping constant] – Damping constant is set at .04– Force = .5 x 8 x 9.8/(0.04) ~ 1000N.

• Acceleration resulting from 1000N vibration force on a 12kg battery– Force = [mass] x [acceleration]/[ξ, the damping constant]– Acceleration = Force x [ξ, the damping constant]/[mass]– Acceleration = 1000N x [.04]/12kg– Acceleration = 3.33m/sec2 or ~.33gn

• 2gn force applied to a 12kg pack– Force = [mass] x [acceleration]/[ξ, the damping constant]– Force = 12 x 2 x 9.8/(.04)– Force = 5880N

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Back-upCalculations

• Force required to shock 0.5kg notebook batteries at 150gn

– Force = [mass] x [acceleration] x Dynamic Amplification Factor – Force = 0.5 x 150 x 9.8 x 2N– Force ~ 1500N

• Acceleration resulting from 1500N shock force on a 12kg battery– Force = [mass] x [acceleration] x Dynamic Amplification Factor – Acceleration = Force / [mass] / Dynamic Amplification Factor – Acceleration = 1500N / 12kg / 2– Acceleration = 62.5m/sec2 or ~6.5gn

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Back-up Aviation Equipment Shock Requirements

• “RTCA, Inc. is a private, not-for-profit corporation that develops consensus-based recommendations regarding communications, navigation, surveillance, and air traffic management (CNS/ATM) system issues. RTCA functions as a Federal Advisory Committee. Its recommendations are used by the Federal Aviation Administration (FAA) as the basis for policy, program, and regulatory decisions and by the private sector as the basis for development, investment and other business decisions.”

• Source: rtca.org

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Back-upRTCA Specification

• DO-160D: Environmental Conditions and Test Procedures for Airborne Equipment

• Shock– “Saw Tooth” configuration pulses– 11ms pulse for standard testing or 20ms for low frequency testing– 18 shocks, 3 per orientation– 6g– Equipment operating

• Crash Safety– Same as above except 1 shock/orientation at 20g