lithium-ion battery survey & safety · advantages 1) higher nominal cell voltages can directly...

© 2019, ALL RIGHTS RESERVED

Lithium-Ion Battery Survey & Safety

Peter McNutt, NREL (PE, MSEE, CESCP, IEEE Sr. Member)

AIHA Rocky Mountain Fall Technical Conference

September 18, 2019

AIHA | 2

1

2

3

4

5

6

7

Introduction / Background

Common Battery Types

Example Battery Systems

Hazards

Standards & Codes Affecting Batteries

How Batteries Are Improving

Risk Assessment

ARVADA AIHA Rocky Mountain Fall Technical Conference2019

Why Be Concerned About Li-ion Batteries & Safety?

As an Electrical Safety Officer I inspect new unlisted research equipment with batteries

We’ve heard the horror stories

(E-cig’s ~ 1-Ah)

How do we know these batteries are safe? 1) Are all batteries prone to explode?

2) What ensures we avoid these incidents?

3) What should you do if a Li-ion battery catches fire?


EV Battery Catches Fire after being towed“Are electric vehicles (EVs) safe? Am I safe parking next to one?”

• EV battery caught fire after being towed to a tire shop (was not in collision) [1 NBC]

• Battery began hissing and ignited

• Fire was extinguished … but hours later reignited

• EV battery fires expected after collisions, but troubling when not in crash [2]

• EV manufacturer recommends flatbed transport and not towing

• Water stream best for extinguishing Li-ion battery fires [4 UL]

• Difficult to spray battery – not easily accessible

• No shock hazard if fought properly

• Gas-powered cars 5 times more likely to experience fire than EVs according to NFPA and NHTSA [3 NFPA]

[1 NBC]


If Li-ion Batteries are so hazardous, why are they so popular?Power & Energy Density

[30]

For a given energy density Li-ion batteries:

• ~ 1/3rd weight

• ~ 1/2 volume


Terminology

• Cell – Single electrochemical unit

• Pack or Battery – Several cells in a single enclosure

• Battery Bank – Multiple cells or battery packs hooked together, usually in series

• BESS – Battery Energy Storage System

• IE – Incident Energy

• UPS – Uninterruptible Power Supply[AO 27]

AIHA | 7

1

2

3

4

5

6

7




Hazards



Risk Assessment


Common Li-ion Battery Types• LCO: 3.6V

• Lithium Cobalt Oxide (LiCoO2)

• LMO: 3.7V• Lithium Manganese Oxide (LiMn2O4)

• LTO: 2.4V• Lithium Titanate (Li4Ti5O12)

• NMC: 3.6V• Lithium-Nickel-Manganese-Cobalt-Oxide (LiNiMnCoO2)

• LFP: 3.2V• Lithium Iron Phosphate (LiFePO4)

• NCA: 3.6V• Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2) [6 BU]

[5 UL]


Li-ion Pros & Cons

Advantages

1) Higher nominal cell voltages can directly power devices offering simplification and cost reduction over multi-cell designs

2) Battery life comparable to life of the equipment

3) Highest capacity per volume & weight

4) Lower maintenance

5) No memory and does not need exercising

6) Simple charge algorithm and reasonably short charge times

Disadvantages

1) Higher initial cost

2) Internal protection circuitry required to prevent thermal runaway

3) Additional transportation regulations

[KC 27 ]


Li-ion Cell Configurations [6]

• Cylindrical• Spiral, Jellyroll construction• Hard can• Lower cost• Reliability may suffer – more interconnections

• Prismatic / Pouch Cell• Wound or stacked layers

• Soft pouch or hard case

• Better reliability

• Lower assembly cost / pack

18650 li-ion cells

18mm dia. / 65mm length

PRV

FYI


Typical Large 12V Storage Battery Construction

• Made from 4 parallel banks of 20 individual cylindrical battery cells

• Monitoring circuit between each parallel bank and for overall voltage and current

• Electronic switch cuts output on command from monitoring module

[KC 27 ]


Electric Vehicle (EV) Li-ion Battery Configurations

• Hundreds of interconnected cylindrical cells

• Prismatic

• Several interconnected batteries

[7] [8]

AIHA | 13

1

2

3

4

5

6

7




Hazards



Risk Assessment


Residential Energy Storage Unit

• 400 Vdc, 7 kWh

• Li-ion NMC battery

• Battery charged by solar array


EV Car Battery• Li-ion battery ~ 375V, 100-kWh

• Nickel, cobalt, aluminum oxide (NCA) battery.

• Higher energy density, more expensive. [9]

[T 2018]

For perspective – no incidents with EVs at NREL: • More than 38 Level-2 EV charging ports • Charging stations installed more than 2 years ago • More than 200+ EV drivers • Every type of EV & PHEV available


BESS Utility-Connected Battery• 18.2-MW Virtual Power Plant

• Connected to Belgian distribution grid

• Frequency regulation – 100 times faster than fossil-fuel plants

• Dispatchable

• Nickel, manganese, cobalt (NMC) battery.

• Lower energy density, longer cycle life, less expensive.

[9][10]

AIHA | 17

1

2

3

4

5

6

7




Hazards



Risk Assessment


Battery Bank Hazards

Four types1. Shock

2. Thermal

3. Arc Flash

4. Thermal Runaway


Shock Hazard

• DC – threshold of 50 Vdc (2018 70E)

• 12, 24, 48 V UPSs – no shock hazard

• Highest voltage for common battery banks – 580 V float voltage

• Class 0 gloves sufficient• Rated 1000 V AC, 1500 V DC

[AO 27]


Can you exceed 50V touching adjacent cells?

20

Cell 54 Cell 2654-26 = 28 cells apart2.0 volts/cell28 x 2.0 = 56 Volts

Is the battery grounded?Touching adjacent grounded metal could also be shock hazard.

[70E 34]


Thermal Hazard

• Historically well known

• TH dominated evolution of safe work practices in UPS work

• Mitigation Methods• Remove jewelry

• Insulated battery tools

• Modular battery bank[AO 27]


Worker suffered 1st and 2nd degree thermal burns to handsCreated a short circuit, bare hands, no PPE

Slide 22

[AO 27]


Arc Flash Hazards

• Arc Flash: An electrical fault that causes ongoing plasma discharge. • Temperatures may exceed 10,000°F.• Arc-rated PPE

• Arc Blast: An electrical explosion that is a function of fault current and containment. [eH 33]

• May injure lungs and ears.

• Incident energy of an Arc Flash or Blast in DC systems is a primarily a function of the fault current and the clearing time. [70E 34]

• In 2006 a worker died from a DC arc flash on a 500-V battery bank. He was not wearing PPE. [LG 32]


Arc-Flash Hazard

• Fault clearing times• Batteries historically used 2-Second Rule or longer

• Could not be switched off

• Li-ion batteries with Internal Fault Protection typically have clearing times < 20 ms leading to lower IE than other types of batteries

[KC 27 ]

• Clearing Time Considerations• External Overcurrent Protection Devices (OCPD)

• Isolate individual battery strings for work or short circuit mitigation

• Safely operable from outside battery cabinet

• Rated for DC

• Limit fault current

• Battery bank disconnects & plugs

• Break battery banks down to safe voltage levels for maintenance


Thermal Runaway Hazard

Ignition of Electrolyte• Overheating electrolyte may cause combustion

• Common cause• Failure of separator between electrodes results in internal short circuit

• Causes may include:• Overvoltage / Overcurrent conditions

• External unprotected short circuit

• External overheating

• Mechanical damage

• Manufacturing defects (dust in clean rooms)


Extinguishing Li-ion Battery Laptop Fire

• FAA YouTube Video – “Extinguishing In-Flight Laptop Li-ion Battery Fire”

• https://www.youtube.com/watch?v=vS6KA_Si-m8

• Extinguishing Options (most to least effective) 2:20

1) Water Extinguisher 3:10

2) Halon Extinguisher followed by Bottled Water 4:30

3) Halon extinguisher alone (does not prevent reignition) 6:10 / 7:10

4) AVOID Ice & Smothering techniques 7:35 / 8:25 / 9:15

Li-ion batteries contain very little lithium metal to react with water(Class D extinguisher should only be used on a Lithium METAL fire) [6 BU]

https://www.youtube.com/watch?v=vS6KA_Si-m8

Extinguishing In-Flight Laptop Computer Fires - Lithium Battery Thermal Runway.mp4


Li-ion – Thermal Runaway Hazards & Safety

• Overheating or overcharging can lead to thermal runaway, cell rupture, or combustion

• Negative terminal produces heat

• Positive terminal produces oxygen• Safety features are required …

Hazards Safety features may include

• Pressure relief valve (cell level)

• fail-safe circuitry (built-in) disconnects the battery when any cell’s voltage is excessive

• Safety features to protect from overheating and internal pressure:• Increase cost

• Another failure point

• If activated - battery inoperable

• Circuitry can drain the battery

[AO 27 ]


Thermal Runaway in Li-ion Batteries• Protection Schemes

• Manufacturing methods• Robust construction and form factors

• Internal mechanical venting (PRV)

• Tested to UL 1642 Standard for Safety Lithium Batteries

• Internal protective circuitry• One-time fuse or resettable solid-state switch

• Overcharge / overvoltage

• Undercharge / undervoltage

• Over current

• Short circuit

• 2 - 20 ms opening times typical[KC 27 ]


• Thermal Runaway for Li-ion Batteries• Protection Schemes

• Physical Isolation• Battery bank physically isolated from facility and

charger/inverter

• Fire rated walls

• Dedicated fire suppression system

• Electrical isolation switch external from battery building/enclosure

[KC 27 ]


Why Are there Li-ion Batteries Incidents?• Exploding phones, cars, laptops, e-cigarettes, etc.

• Billions of consumer products using these batteries every day • (incidents statistically small but high-profile events) [CR 11]

• High energy density (100’s of Wh/kg) stored in anode and cathode, separated by a very thin, delicate (10µ) permeable polyethylene separator, with a liquid electrolyte - a solvent containing lithium salts - that enables the electric charge to flow

• When the separator is breached or melts, short circuit occurs which starts thermal runaway – usually manufacturing issue or mechanical damage

• Temperatures may reach more than 1,000° F at which point the flammable electrolyte ignites or explodes when exposed to oxygen in the air


Are EVs More Dangerous Than Gas Cars?

• EVs statistically not as likely to catch fire …

• One EV manufacturer claims have 300,000 of their vehicles on the road that have been driven a total of 7.5 billion miles, and about 40 fires have been reported -about 5 fires for every billion miles traveled, compared to a rate of 55 fires per billion miles traveled in gasoline cars. [CNN 12]

• Research being conducted on new battery materials

• 130 years spent improving safety of gasoline systems

• Battery fires make for good headlines


Li-ion Battery Ignition & Reignition

Issues

• Battery fires may be very intense and difficult to contain

• Battery fires may seem fully extinguished yet reignite hours or even days later [NFPA 3]

• How do firefighters know when the fire is completely extinguished?

• Peculiar to Li-ion batteries & not fully understood

• Researchers looking for nonflammable electrolytes


Transportation Safety Concerns• Li-ion Shipping

• Li-ion air shipping limitations –• IATA Class 9 “Misc. Dangerous Goods”

• Limited SOC (State of Charge) for shipping

• Expect longer delivery times and/or higher shipping costs

• Shipping charges may be offset by lower weights on batteries

• Other battery types• FAA notes Li-ion only involved in 27% of battery incidents

• Other types of batteries can cause fire due to faulty packaging leading to electrical short circuit and heating

• Lead-acid wet-cells Class 8 “Corrosives”[KC 27 ]

REQUIRED LABELS


What to do if a Li-ion Battery Overheats, Hisses, Bulges or Catches Fire

1) Unplug from charger

2) Move device away from people and flammable materials

3) Avoid picking up device (too unpredictable)

4) Extinguish fire

5) Douse cell or battery with WATER try to prevent Thermal Runaway & Reignition

6) May need to let battery burn itself out [BU 6]

AIHA | 35

1

2

3

4

5

6

7




Hazards



Risk Assessment


Standards Affecting Battery Design

• UL 1642 (2012) Standard for Lithium Batteries

• UL1973 Stationary batteries • typically energy storage batteries for solar/photovoltaic systems or

they store energy from the grid and turn on during peak times or during power loss

• UL2271 for light electric vehicle such as scooters, wheelchairs, material handling equipment

• UL2580 EV (larger) batteries

[Inv 14]


UL 1642 Tests include

Battery only passes if…

NO FIRE

NO EXPLOSION

• Electrical Testing• Short Circuit at room temperature and high

temperature• Abnormal Charge• Forced Discharge

• Mechanical Testing• Crush• Impact• Shock• Vibration

• Environmental Testing• Heating• Temperature Cycles• Low Pressure

• Fire Exposure Testing• Projectile

UL 1642 tests being conducted in ESIF for clients – extremely high reliability required


Determine if a Battery is UL Listed

[K2 29]

UL 1642


Standards Affecting Battery Transport

• UN DOT 38.3 [16] Tests for Cells & Batteries - similar to UL 1642

• IATA [28]: International Air Transport Association (Dangerous Goods Regulations)

• Lithium Metal (non-rechargeable) – forbidden to be shipped by themselves as cargo on passenger aircraft.

• Lithium Ion (rechargeable) – only allowed to be shipped as cargo at a SOC < 30% of rated capacity

• TSA [15]: Battery larger than 100 Wh (some power tools now exceed this)

• Checked Baggage? NO• Carry-On Bags? YES Limited 2 spares per passenger – with airline approval


Standards & Codes Affecting Battery Installations

• UL 9540A (2018) - Test Method for Evaluating Thermal Runaway Fire Propagation in BESS

• IFC (2018) – International Fire Code

• NFPA 1 (2018) – Fire Code

• NFPA 68 (2018) - Standard on Explosion Protection by Deflagration Venting

• NFPA 855 (proposed) - Standard for the Installation of Stationary Energy Storage Systems

• IEC and IEEE – numerous standards

• NFPA 70E (2018) - Standard for Electrical Safety in the Workplace

• NEC (2017) – National Electrical Code

AIHA | 41

1

2

3

4

5

6

7




Hazards



Risk Assessment


What’s Being Done To Improve Battery Safety?

• United States Advanced Battery Consortium established standard battery testing procedures that are widely adopted • NREL, INL, ANL, ORNL, USCAR

• Improve Abuse Tolerance (new & used batteries)

• Reduce Failure propagation [18]

• NREL inventions for improving Li-ion battery safety in “NREL Battery Technologies Available for Licensing” [31]


Li-ion battery you can safely cut with scissors

o Tufts University professor Mike Zimmerman – background in plastics began searching for a safer electrolyte

o Reporter cuts the battery with scissors while battery continues to provide power with no ill effects

o No mention of the availability or energy density of the new “safe” battery

o Video also shows footage of “conventional” LI batteries being poked or cut causing them to burst into flames

o Two-minute YouTube video:https://www.youtube.com/watch?v=m9-cNNYb1Ik

o “Conventional” li-ion batteries damaged & exploding 1:00

o New “safe” li-ion battery being cut up & operating 1:25 - 2:00 NOVA WGBH 2017

The Battery That Refuses to Explode NOVA.mp4

The Battery That Refuses to Explode NOVA.mp4


Minimize & Eliminate Li-ion Battery Explosions1) Use only original or equivalent charger

• Beware of cheap imitations!

2) Do not modify the battery or charger

3) Dispose of batteries if they become hot, swell, or show any signs of damage

4) Letting batteries charge continuously [without regulating circuitry may be risky][BBC 19]

5) “Hazardous especially if they are modified, damaged, or of dubious origin (suspect or counterfeit batteries)” [KT 20]

AIHA | 45

1

2

3

4

5

6

7




Hazards



Risk Assessment


Risk Assessment: Battery Procurement

• Procurement Considerations• Temperature Limitations – if temperature is too high or

too low, some chemistries may not be viable.

• Protection Circuits – may be needed if not provided with battery

• Charging Requirements – would a new charger be required or could an existing charger be used

• Transportation Limitations – may increase cost and time for delivery

[AO 27 ]


Risk Assessment: Battery Design

• Design Considerations• Overcurrent Protection – can the battery be

isolated locally; arc flash energy reduction• Fire Concerns – can heat be adequately

removed• Non-interchangeable Connectors – can

cells/packs be connected incorrectly• Shock Hazards – exposed energized components

located such that they do not pose shock hazards

• Charger Modifications – adjust charger to proper profile for new battery

[AO 27 ]


Risk Assessment: Installation / Maintenance

• Installation and maintenance considerations:• Thermal Hazard – Tools capable of shorting between

terminals, cells, or ground (use insulated tools)

• Shock Hazard – if working within RAB of energized components > safe voltage, proper PPE required

• Arc Flash Hazard – if arc flash hazard exists, wear arc-rated PPE

[AO 27 ]


Risk Assessment: Battery Bank Pre-Job Briefing

• Battery task specific considerations:• Hazard Recognition - ensure workers understand all hazards

• PPE Requirements - discuss what PPE to wear

• Float or Grounded – is the battery grounded?• Could pose a shock hazard to adjacent grounded metal

[AO 27 ]


BESS Tested At NREL –Lesson Learned• System integrator contracted NREL to test

functionality of their new system

• Sea container converted into BESS

• Lacked panic (egress) hardware NEC 110.26(C)

• No windows

• Maintenance required turning off 120 V charging system and lights NEC 110.26(D)

Battery:

• Chemistry: LFP

• Voltage / Capacity: 384 Vdc, ~ 100 kWh


BESS Tested

At NREL…Lesson Learned:

• Connectors:• Interchangeable• Not keyed• Not labeled• Not color coded

• No OCPD in modules

Guess what happened?


Concluding Thoughts• Li-ion batteries have attributes that make them desirable for power and energy

applications (intermittent wind and solar become dispatchable)

• Many different Li-ion batteries on the market – not all the same

• Batteries must be used per the manufacturers’ instructions: • charge / discharge / environment

• Systems should be well engineered

• Arc-flash hazard of Li-ion batteries found to be less than that of other types due to internal protective circuitry

• Batteries continually being improved

• Hope this dispelled myths & misinformation


Acknowledgements

• Kyle Carr – LANL

• Andrew Olsen - elecTrain

• Heath Garrison – NREL

• Greg Martin – NREL

• Robert Backstrom – UL

• Alex Klieger – UL

• Kandler Smith – NREL

• Michael Wray – K2 Energy

• Lloyd Gordon – LANL

• Tommy Martinez – LANL

• Jennifer Martin – FE&C

This work was supported by the U.S. Department of Energy under Contract No. DE-AC36-08GO28308 with Alliance for Sustainable Energy, LLC, the Manager and Operator of the National Renewable Energy Laboratory.

The views expressed herein do not necessarily represent the views of the DOE or the U.S. Government.


References 1

[1] https://www.nbcbayarea.com/news/local/Tesla-Vehicle-Catches-Fire-in-Los-Gatos-503080661.html

[2] https://electrek.co/2018/12/19/tesla-model-s-fire-towing/

[3] J. Roman, The Lithium-ion Conundrum, NFPA Journal, January/February 2016.

[4] R. Backstrom & A. Klieger, UL, personal email, 1/15/19.

[5] A. Barowy, P. Gandhi, UL 9540A – Test Method for Evaluating Thermal Runaway in Battery Energy Storage Systems, UL Webinar, August 2018.

[6] Battery University, Cadex Electronics, https://batteryuniversity.com/

[7] https://hackadaycom.files.wordpress.com/2014/09/tesla-batt.jpg?w=800

[8] https://inhabitat.com/will-the-nissan-leaf-battery-deliver-all-it-promises/?variation=c

[9] http://fortune.com/2015/05/18/tesla-grid-batteries-chemistry/

[10] https://www.greentechmedia.com/articles/read/tesla-restore-powerpack-balance-grid-virtual-power-plant

[11] A. St. John, Why Lithium-Ion Batteries Still Explode and What's Being Done to Fix the Problem?, Consumer Reports, Sept. 21, 2016.

[12] Chris Isodore, Are Electric Cars More Likely To Catch Fire?, CNN Money, May 17, 2018.

[13] Lithium-ion Battery Energy Storage Systems – The Risks and How To Manage Them, AIG Energy Industry Group, January 2018.

[14] [Inventus] Medium Format Li-ion Battery Design Guidelines – White Paper, Inventus Power, May 2017.

[15] https://www.tsa.gov/travel/security-screening/whatcanibring/items/lithium-batteries-more-100-watt-hours

[16] UN Manual of Test and Criteria, section 38.3 Lithium Batteries, and the related Dangerous Goods Regulations, International Air Transport Association (IATA).

[17] https://www.faa.gov/about/office_org/headquarters_offices/ash/ash_programs/hazmat/passenger_info/media/Airline_passengers_and_batteries.pdf


References 2[18] C. Orendorff, et al, Battery Safety Testing, SNL, DOE, June 2014.

[19] L. Ives, BBC News, How Likely Is Your E-Cigarette To Explode? 18 May 2018.

[20] K. Taylor, Email, NREL, 2/5/19.

[21] K. Carr, Clearing Time Considerations for DC Arc Flash Hazard Analysis for Battery Banks, IEEE ESW, Fort Worth, TX, 2018.

[22] D. Doan, “Arc Flash Calculations for Exposures to DC Systems,” IEEE Transactions of Industry Applications, Vol. 46, No. 6, November/December 2010.

[23] https://efcog.org/best-practices/ #194

[24] DOE Handbook – Electrical Safety, July 2013.

[25] S. Kukkonen, Current Trends in Battery Technology, ECV National Seminar, VTT Technical Research Centre of Finland, September 2014.

[26] Panasonic Batteries Nickel Cadmium Batteries Technical Handbook ‘99, Matsushita Battery Industrial Co., Ltd., 1999

[27] Battery Safety Training, ElecTrain LLC., A. Olsen, January 2018

[28] 2019 Lithium Battery Guidance Document, IATA, 2019 Rev. 1

[29] M. Wray, K2 Energy, telephone call and email, April 2, 2019.

[30] https://medium.com/solar-microgrid/battery-showdown-lead-acid-vs-lithium-ion-1d37a1998287

[31] NREL Battery Technologies Available for Licensing, December 2016.

[32] L. Gordon, et al., Electrical Injuries and Fatalities: Facts, Myths, and Unknowns, IEEE ESW, 2019

[33] Low Voltage QEW-2 Workbook, e-Hazard, 2018.

[34] NFPA 70E Standard for Electrical Safety in the Workplace, 2018.


Other Sources

[S1] Researchers Build Nonflammable Lithium Ion Battery, Electric Vehicle Research, February 12, 2014.

[S2] K. Smith et al, Battery Technologies for Heavy Duty EVs, NREL, APTA Webinar, August 19, 2015.

[S3] Matt Ferrell, YouTube, Electric Cars Myths vs. Facts, Jan. 2019.

[S4] P. McNutt, A. Olsen, K. Carr, Risk Assessment Methods for Battery Bank Thermal, Shock and Arc Flash Hazards, IEEE ESW, Jacksonville, FL, IEEE ESW 2019 T5.

lithium-ion battery survey & safety · advantages 1) higher nominal cell voltages can directly...

Documents