B ATTERIES : R ISKS AND R EALITIES DAV I D RAH E, CRE R EALITY : B - - PowerPoint PPT Presentation

BATTERIES: RISKS AND REALITIES

DAV I D RAH E, CRE

REALITY: BATTERIES POWER OUR LIVES

Portability is reality……always moving toward greater mobility Battery energy is the means to power portability, but what are the risks?

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2 This isn't your grandpa’s battery!

Li I on Battery Projected Growth

CHALLENGES

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Batteries rely on an electrochemical process … limitations will prevail. How to get the most out of the electrochemical device?

New Chemistries

Meet these demands: Under these conditions:

 Temperature  Temperature shock  Vibration  Humidity  Altitude  Random Drops  Impacts  Immersion & more  Longer Runtime  Greater Charge / Discharge Cycle Life  Lower Cost  Smaller Size  Quick Charge Time

• Secondary cells

 More Power  Green – Environmentally Friendly  AND Safe

Lead Acid

• Developed in 1890
• Larger power applications where weight is of little concern; car starter battery, hospital equipment, wheelchairs,

emergency lighting and UPS systems. Nickel Cadmium (NiCd)

• Developed in 1947
• Mature and well understood but relatively low in energy density
• Contains toxic metals
• Periodic full discharge is critical, if omitted, large crystals form on the plates
• Long life, high discharge rate and economical
• Two-way radios, biomedical equipment, video cameras and power tools

Nickel-Metal Hydride (NiMH)

• Developed in 1990
• 50% higher energy density compared to the NiCd
• Reduced cycle life
• High self discharge
• Contains no toxic metals
• Digital cameras with LCDs and flashlights

Lithium Ion (Li-ion)

• Developed in 1991
• Fastest growing battery system
• Li-ion is used where high-energy density and lightweight is of prime importance
• The technology is fragile and a protection circuit is required to assure safety
• Notebook computers, EV cars

Lithium Ion Polymer (Li-ion polymer)

• Developed in 1994
• Offers the attributes of the Li-ion in ultra-slim geometry and simplified packaging
• Mobile phones, tablets

REALITY: CELL CHEMISTRIES

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REALITY: CELL CHEMISTRIES

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Best Solution: Lithium Ion

BEST SOLUTION: LITHIUM ION

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Highest Energy densities (smaller and lighter), Higher Voltage, no Memory Expected to dominate the market by 2017.

Technology :

• Lithium-ions move through an electrolyte from the negative electrode (“anode”) to the positive

electrode (“cathode”) during battery discharge, and from cathode to anode during charging.

• The electrochemically active materials in lithium-ion batteries are typically a lithium metal oxide for

the cathode and a carbon for the anode.

• Cathode options: Li-cobalt, Li-manganese, Li-iron phosphate, Nickel-manganese-cobalt, Lithium

Thionyl Chloride (high temp), others

• Electrolytes can be liquid, gel, polymer or ceramic.

Technology improvements are expected to further increase cell performance.

18650 Can

RISKS: LITHIUM ION

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Request to Stop Using VAIO Fit 11A/Flip Personal Computer Posted: 4/11/2014 Dear Valued Sony VAIO Customers, It has come to our attention that some of the internal, non-removable battery packs provided to us by a third-party supplier and included in 368 units of VAIO Fit 11A/Flip PC released in February 2014 have the potential to

• verheat resulting in partial burns to the housing of the PC.

If you have one or more of the VAIO Fit11A/Flip PC model listed below, please immediately discontinue use, shut down and unplug the PC. We are currently identifying…………… Lenovo was forced to recall over 150,000 battery packs for its popular ThinkPad line earlier this year after discovering systems can overheat, posing a fire hazard, said the U.S. Consumer Product Safety Commission HP Expands Recall of 280,000 Notebook Computer Batteries Due to Fire Hazard BatteriesPlus Expands Recall of Battery Packs used with Cordless Tools Due to Explosion Hazard. The replacement battery pack can explode unexpectedly, posing a risk of injury to consumers. Boeing 787 Dreamliner's first year of service, at least four aircraft suffered from electrical system problems stemming from its lithium-ion batteries. Tesla Model S; road debris punctures undercarriage, crash. 6,500 LIBs in 16

• modules. Tesla S & Chevy Volt sitting in a

garage Sony 6 million recalled

SAFETY: HOW TO MITIGATE RISK

Pack a lot of chemical energy into a small space and if something goes wrong, fire or explosions are the inevitable result.

Can it fail safely?

• Cell Safety features
• PTC (Positive Temp Coefficient) thermistor
• Over charge pressure sense, CID (Current Interrupt Device)
• Over discharge sleep
• Pressure relief vent
• Battery Management Systems
• Communicates with other components, to limit the current they source or draw
• Manages charge

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Anode short to Cathode

SAFETY: HOW TO MITIGATE RISK

Pack a lot of chemical energy into a small space and if something goes wrong, fire or explosions are the inevitable result.

How does the industry test for safety?

• Numerous Test Standards that focus on specific risk from

electrical, mechanical and environmental conditions

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Tests:

• External short circuit
• Abnormal charge
• Forced discharge
• Impact
• Shock
• Vibration
• Heating
• Temperature Cycling
• Low Pressure (Altitude)
• Drop
• Penetration
• Immersion

Anode short to Cathode

SAFETY: TESTS

Underwriters Laboratories

• UL 1642: Lithium Batteries
• UL 1973: (Proposed) Batteries for Use in Light Electric Rail (LER) Application and Stationary Applications
• UL 2054: Household and Commercial Batteries
• UL Subject 2271: Batteries For Use in Light Electric Vehicle Applications
• UL 2575: Lithium-Ion Battery Systems for Use in Electric Power Tool and Motor Operated, Heating and Lighting Appliances
• UL Subject 2580: Batteries For Use in Electric Vehicles

Institute of Electrical and Electronics Engineers

• IEEE 1625: Rechargeable Batteries for Multi-Cell Mobile Computing Devices
• IEEE 1725: Rechargeable Batteries for Cellular Telephones

National Electrical Manufacturers Association

• C18.2M: Part 2, Portable Rechargeable Cells and Batteries — Safety Standard

Society of Automotive Engineers

• J2464: Electric and Hybrid Electric Vehicle Rechargeable Energy Storage Systems (RESS), Safety and Abuse Testing
• J2929: Electric and Hybrid Vehicle Propulsion Battery System Safety Standard — Lithium-based Rechargeable Cells

International Electrotechnical Commission

• IEC 62133: Secondary Cells and Batteries Containing Alkaline or Other Non-acid Electrolytes — Safety Requirements for Portable Sealed

Secondary Cells, and for Batteries Made from Them, for Use in Portable Applications

• IEC 62281: Safety of Primary and Secondary Lithium Cells and Batteries During Transportation

United Nations (UN)

• Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, Part III, Section 38.3

Japanese Standards Association

• JIS C8714: Safety Tests for Portable Lithium-Ion Secondary Cells and Batteries For Use In Portable Electronic Applications

Battery Safety Organization

• BATSO 01: (Proposed) Manual for Evaluation of Energy Systems for Light Electric Vehicle (LEV) — Secondary Lithium Batteries

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TESTS: PERFORMANCE

Life Cycle Tests (electrical)

• Battery Manufacturer provides test data at 25C
• Single charge/discharge is generally defined as one cycle. The process is repeated until

state of charge fades to a predetermined level (80% of initial capacity). Target ≈400+ cycles or EOL.

• Other stresses applied

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The choice of battery in an application is driven by:

• Application requirements for power and energy
• Cost
• Physical characteristics (i.e., size, shape, weight, etc.)
• Life required by the application
• Anticipated environment in which the product will be used
• Anticipated duty cycle of the product (continual or intermittent)
• Maintenance and end-of-life considerations

Test for the Application: mimic electrical, mechanical and environmental conditions Safety tests are critical but in the product…the OEM’s design controls the battery!

TESTS: CELL FAILURE MECHANISMS

Fatalities may be due to:

• Short circuits resulting from contaminated materials
• Mechanical tolerance problems, burrs, dendrites, and Lithium plating
• Open circuits caused by broken welds, loose connections, or cracks
• External faults such as BMS failures can also cause failures in the cells they are supposed to protect

Examples of wear-out failures are:

• Dendrite growth, formation of small crystals structures around the electrodes and can pierce the separator

causing a short circuit

• Lithium plating of the anode
• Chemical electrolyte loss through evaporation
• Electrolyte dry-out
• Cathode material dissolves
• Moisture ingress due to vent failure or case seal failure
• Cracks in the active materials or the cell case
• Passivation, a resistive layer builds up on the electrodes impeding the chemical action

Wear-out failures are generally due to the gradual deterioration of, or reduction in, the active chemicals resulting in reduced cell capacity. Batteries deteriorate whether they are used or not.

• Time and temperature related damage affects chemical and physical properties that deteriorate the

internal impedance and decrease the energy storage capacity. The relationships can be modeled with the Arrhenius law since empirical evidence suggests that the rate of increase in internal impedance rate

• f deterioration doubles with every 10°C increase in temperature.

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Key Test Attributes:

• Prove 20 years life
• Cell Chemistry: Lithium Thionyl Chloride, AA cells
• Primary: Non-rechargeable
• Sample Size: 60 from 2 different lot codes
• Duration: 2-3 months
• Application: Outside installation, RF pulse 4 times/day, 7.2mA & 30 second pulse
• Accelerants: Time (frequency of the current pulses), Energy and Temperature

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EXAMPLE: ACCELERATED LIFE TEST

Battery Discharge Test Equipment

• Arbin BT2000 Battery Charge / Discharge System
• Agilent 34980A Dataloggers
• Precision Loads

Test Plan

Results:

• 3 cells failed due to early storage capacity loss / wear-out
• Intermittent failures of vertical oriented cells
• Weibull analysis based on the 3 failures provided inconclusive results:
• Unrealistic mean life estimate of 63 years
• No characteristic trend of rapid capacity loss

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EXAMPLE: ALT RESULTS

Results:

• ALT was continued to better determine wear-out
• Resulting in 22 additional failures with proper capacity fade drop-off beyond 21 years
• Weibull analysis based on the 25 failures;
• Improved result confidence, calculated mean life estimate of 23.5 years
• Beta value of 12, corresponds to aggressive wear-out / end-of-life period
• Prediction of 90% failure after 26 years
• Cells subjected to the testing met the customer target requirement of 20 years’ service

life at 90% reliability with a 50% confidence.

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EXAMPLE: ALT EXTENDED RESULTS

David Rahe, ASQ CRE

12317 Technology Blvd. Suite 100 Austin, TX 78727 512-775-4001 drahe@AustinRL.com www.AustinRL.com

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Thank You