Vibration and Shock Testing Requirements

UN 38.3 Lithium-ion Battery Testing
Topics
• 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 Requirements
KEY 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 Tests
UN 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 1g n
; amplitude decreasing
– 18Hz to ~50Hz with 0.8mm amplitude; acceleration increasing to 8g n
– ~50Hz to 200Hz at 8g n
; amplitude decreasing
– 200Hz to ~50Hz at 8g n
; amplitude increasing
– ~50Hz to 18Hz with 0.8mm amplitude: acceleration decreasing to 1g n
– 18Hz to 7Hz at 1g n
; 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 g n peak acceleration, 0.006 seconds pulse duration
– Large batteries: Half-sine, 50 g n 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 Batteries
Mild 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 Batteries
Mild 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 Batteries
Typical 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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• 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 Testing
Issues 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 Testing
Test 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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• 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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• UN T3 testing of HEV batteries at these frequencies and
8g n 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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• T3 Test Recommendation For batteries > 12kg:
– Reduce force level from 8g n to 2g n
• Basis for recommendation
– Force levels are more realistic and exceed current exerted forces.
» Force required to vibrate cell and notebook batteries at 8g n
~1000N
» 1000N applied to vibrate a mild hybrid battery is ~0.33g.
– 2g n is equivalent to 5880N for a 12kg pack
– 9 hours of swept-sine vibration testing at 2g n large battery. is still a severe test for a
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• 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 150g n
~1500N
» 1500N applied to shock a mild HEV battery (~500Wh, 12Kg) is ~6.5g
n
.
– There is no source for the additional 38,000N.
– Aviation specifications (RTCA) test for Crash Shock at 20g maximum.
• Recommend limiting acceleration to 50g n
– Far exceeds realistic and expected levels
– 50g n for all batteries > 12 kg already is used in UN 38.3 for large batteries.
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• 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
HEV Lithium-ion Battery Transportation Scenarios
• Prototype or Development Stage
1. Battery transported from manufacturer to airport by vehicle
2. Airport to airport
3. Airport to distribution center by vehicle
4. Distribution center to HEV system integrator by vehicle
5. HEV system from system integrator to OEM engineering by vehicle
6. HEV (car) from OEM engineering to test site by vehicle
7. HEV (car) back from test site to OEM engineering by vehicle
8. HEV system from OEM engineering back to integrator by vehicle
• Production Stage
1. Battery transported from manufacturer to marine port by vehicle
2. Marine port to marine port
3. Marine port to distribution center by vehicle
4. Distribution center to HEV system integrator by vehicle
5. HEV system from system integrator to OEM assembly plant by vehicle
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Back-up
Calculations
• Resonant Vibration Force at 8g n
– 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 150g n
– 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-up
Vibration Isolation
Mass of Pack
K Stiffness of battery
In testing, vibration is transmitted to the battery depending on the stiffness of the battery.
K test
= K battery
In reality, vibration is transmitted depending upon the stiffness of the container, the packaging and the battery.
K equivalent
= 1
1 + 1 + 1
K battery
K packaging
K container
Mass of Pack
K Stiffness of battery
●
K p
Stiffness of packaging
●
K c
Stiffness of container
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Back-up
Calculations
• Stopping a wrecking ball examples:
– 550kg wrecking ball after falling 1sec in 1 meter
– Force avg x distance = mass x velocity 2 /2
– Force avg
– Force avg
= (mass x velocity
= 550kg x (9.8m/s)
– Force avg
= 26411 kgm/s 2
2
2
) / (2 x distance)
/ (2 x 1m)
– Force avg
= 26411N
– 550kg wrecking ball after falling 1sec in 0.28 meters
– Force avg
– Force avg
– Force avg x distance = mass x velocity
= (mass x velocity
= 550kg x (9.8m/s)
– Force avg
= 94325 kgm/s 2
– Force avg
= 94325N
2
2
2 /2
) / (2 x distance)
/ (2 x 0.28m)
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Back-up
Calculations
• 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/sec 2 or ~.33g
n
• 2g n 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-up
Calculations
• Force required to shock 0.5kg notebook batteries at 150g n
– 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/sec 2 or ~6.5g
n
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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-up
RTCA 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
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