108 bestsafety UL Underwriters Laboratories

Tracking battery safety
right from the start
UL has been setting the standards on battery safety whenbatteries starting becoming more ubiquitous nearly 40 years ago.
Laurie Florence, UL’s Principal Engineer for Motive/Stationary
Batteries, Energy Storage, Fuel Cells, and Capacitors reveals thehistory of battery standards developments.

As a premier standards
development and safety
certification organisation,
UL has been involved in battery
safety since the 1970’s, startingwith battery chargers (UL 1236) andin the 1980’s publishing one of thefirst battery safety standards, UL
1642, for primary (non-rechargeable)lithium batteries followed byinclusion of requirements forsecondary (rechargeable) lithium
batteries (including lithium-ion).
UL continues to be a leader insafety for the battery industry,
which has come a long way. This
includes utilisation of new battery
technologies, many new battery
applications, and facing new safetyissues with the increased use ofbattery operated products.
The evolution of battery use
through past decades has seena change from the use of more
traditional technologies such aslead-acid and Ni-Cd, to increasinguse of lithium-ion. Use has also
grown to include not only portableapplications, but motive andstationary as well. In addition,battery standards have evolved froma more generic safety approachto the unique needs of specificbestmagazine // Summer 2016

applications. This issue was brought
to light in the well-publicisednotebook computer battery recallsof 2005 through 2006. The result ofthe findings from those large-scale
recalls highlighted the reality thatthe high-tech industries’ need forincreased energy in an increasingly
smaller footprint reduced thesafety margins of the cells used inthose products. As a result, a small
contaminant in the cell introduced
during production could result in
the potential for catastrophic fieldfailures. This realisation drove theindustry and standards developers
to drive battery standards forward,
and come up with ways to betteralign the end product applicationand the battery used to power thatapplication.
This experience also led UL totake a deeper look into the actualinternal cell construction as partof the safety certification of thecell. UL helped industry improverequirements in UL 1642 (evolvedto be only a portable lithium cellstandard) and UL 2054 (portablelithium/nickel battery packs & nickelcells) including the certifications
associated with those standards.
UL then built off these concepts inother applications of batteries suchas the portable tool industry.
The portable-tool and applianceindustries, which were becoming
increasingly reliant on lithium-iontechnology, approached the issueof battery safety for their industries
by partnering with UL to develop
UL 2575 in February 2011, later
replaced by UL 2595 in May 2013.
UL 2595, is a ‘horizontal’ standard
that coordinates evaluation of thebattery system of the particular
tool or appliance. The criticaldevelopment was to look at thecombination of battery, charger andend-product using both UL 2595
requirements and the particular
end-product standard requirements
pertaining to the battery in orderto determine that the system
maintains the battery within its
safety limits. This system approachto battery safety is necessary inorder to help ensure that all partsof the electrical system effecting
battery safety are evaluated
together to validate the safety ofthe battery system.
As for the motive and stationary
applications of batteries, it wasaround 2008 that the use of lithiumion batteries in these applications,

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Underwriters Laboratoriesbestsafety 109

such as electric vehicles, gained
public notice. Up until this time,
the batteries used in vehicles wereprimarily lead-acid for starting,lighting and ignition (SLI) andnickel metal hydride in hybrid
electric vehicle (HEV) applications.
The automotive industry began
manufacturing vehicles morereliant on battery motive powersuch as plug-in hybrid electricvehicles (PHEVs) and battery electricvehicles (BEVs), as lithium-ion
batteries provided sufficientenergy density to be a practicalsolution for commercialisation.
Although lithium-ion has thebenefit of being one of the mostenergy-dense commerciallyavailable technologies, it also has
a reputation for safety issues due
to ongoing field incidents that
continued to make headlines.
Regulators and the general public
need to have a level of confidence
to accept these new technologies,
which involve a very energydense battery in a large andcomplex system. There was also
the issue of new players, outsideof the traditional vehicle OEMs,
developing electric vehicles that
may have lacked the experienceand resources to build a safe
battery system. To address theconcerns for safety, and becauseof UL’s experience with evaluating
lithium-ion batteries over the years,
UL published UL Subject 2580 inNovember 2009 to address safetyof batteries for EV applications.
This later became the American
National (ANSI) consensus Standard
in October 2011 and a bi-national
standard for the USA and Canada
in December 2013. In December of2013, UL also published the ANSI/
bi-national standard UL 2271 for theUSA and Canada, which addresses
light electric vehicle battery

UL’s Battery andEnergy Storage
Technology (BEST)
test centre, locatedat the Battery
Innovation Centre,
is poised toadvance the futureof energy and theelectrical grid.

safety. This includes batteries
for such diverse applications
as motorcycles, wheelchairs orbicycles and other small motiveapplications. UL 2580 and UL 2271
are not technology specific, butthey do include requirements forlithium-ion batteries and addressconcerns specific to the types ofenvironments and abuses thesemotive applications may encounter.
Although UL 2580 and UL 2271
are specifically battery standards
and do not include the charger
requirements or other aspects ofthe vehicle electrical system, they
address the safety of the battery
management system (BMS) andrequire that the BMS along withany other protection controls
in the battery system maintainthe batteries in their specified
operating region for voltage,temperature and current. Thisis critical for safety of all battery
technologies but especially so forlithium-ion batteries that needto tightly control the voltage andtemperature limits of the cells.
These standards require a safety
analysis of the battery system suchas a failure modes and effects
analysis (FMEA) and that electronics
and software relied upon for safety
are evaluated for functional safety.
The FMEA needs to determine
necessary performance level ofthe controls, which in turn impacts
the scope of the functional safety
investigation. The functional safety
investigation of electronic controls
consider single fault conditions andenvironmental stresses such as
EMC, vibration, high temperaturestress, temperature variation, etc.
The software controls are evaluatedfor risks associated with both
systematic faults due to software
defects and random faults due tofailures of microelectronics.
Just as lithium-ion batteries andother unique technologies are being

bestmagazine // Summer 2016

110 bestsafety
utilised in new applications suchas vehicle motive applications,
stationary applications andenergy storage applications thereis less field experience and lessinformation on the safety of thesesystems. Besides lithium-ion
batteries, these stationary
applications are less constrained bylimitations for weight or even size insome cases and can consider more
exotic technologies such as moltensalt batteries and flow batteries. To
address these various technologies
and stationary battery safety, UL
developed UL 1973 in July 2010 andlater became an ANSI consensus
standard in February 2013. UL 1973
continues to be in the forefront ofsafety for battery systems for theseapplications, and its inclusion ofrequirements for these various
battery technologies was well inadvance of other efforts to address
stationary battery safety. Like theprevious motive battery standards,
UL 1973 requires a safety analysis
such as an FMEA and includes
requirements for functional safety
if electronics and software are
identified as critical to the battery
system safety. Similar to UL 2580,
UL 1973 also requires a propagation
test for some technologies suchas lithium-ion, where there is thepotential for defects in productionthat could result in catastrophic
failures not controllable byelectronics in the field. The
requirements evolved from UL’s
deep knowledge of battery safety,
learnings from evaluation ofunique stationary
battery systems
and input from thestandards technicalpanel members,
which includes abalanced mix ofmanufacturers, usersof the technologies,
government entities,authorities having jurisdiction, andother organisations. UL 1973 has
bestmagazine // Summer 2016

gone through additional revisions
since it was published in 2013 toaddress additional learnings that
included major revisions publishedin June 2016 such as stationary
lithium cell criteria. Since its
publication, UL 1973 has been the
go-to-standard for certificationof these stationary systems andcomponent packs and modules
intended for stationary systeminstallations. It has provided theindustry, customers and regulatorswith a level of comfort that thesestationary systems are safe forinstallation.
From UL 1973, it was a natural
progression to development of UL
Subject 9540 for energy storage
systems in July 2015. This standard
addresses the unique concernsof energy storage systems. This
includes battery safety and grid/
wiring system connectivity, as
well as issues such as balanceof plant components, HVAC andlighting systems and fire detection
and suppression systems, andwork space and life safety criteria
applicable to walk-in systems. UL
9540 looks at the safety of thesevarious critical components in
a complete system, and like theother standards utilises safety
analysis, component criteria andtesting to evaluate for safety.

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Again, UL was in the forefront ofsafety standards development
and safety certification of thesecomplete systems. UL 9540 stands
out as a pioneering document toprovide a framework for evaluating
safety of energy storage systems
and covers not only battery systems
but mechanical, chemical and even
thermal energy storage systems.
UL 9540 is in the process of being
finalised as an ANSI and bi-national
standard for the USA and Canada.
Through these efforts, UL has
offered the industry a means
to validate the safety of theirsystems to promote acceptance.
This continued with the effort toaddress hoverboard safety withthe publication of UL 2272 in amatter of weeks. UL is now able tocertify products to UL 2272, andsome products that caused global
concern are now certified by UL forsafety, providing the public withease of mind. UL 2272 is scheduled
to be finalised as an American andCanadian National standard within a
few months.
UL has taken the initiative toaddress the safety of batteries, andthe industry, retailers andconsumers alike have benefited
from UL’s efforts. Batteries are partof our world and they have been
gaining traction as a way forproviding reliable power, cutting theplug and reliance on fossil fuels. UL
continues to be actively been
involved in leading the efforts toaddress the safety of this evolving
industry. From our battery research
activities, to development ofbattery safety standards, toexperience evaluating
batteries for certification,
to our outreach toretailers, regulators andconsumers— UL has beena champion for battery
safety for decades and welook forward to continuing topromote safe battery
technologies.