Batteries to Blame in RC Helicopter Fires

On Wednesday (09/10/08), yet another remote controlled
toy helicopter was recalled – the eighth one this year and the ninth associated
with fire and burn hazards since 2006.  The
culprit in nearly every case?  Rechargeable Lithium
batteries and/or their chargers.  As I examine
my 10-year-old son’s version of a flying copter (above), which I took away at
about recall number five despite it not being on the recall list, I wonder how
long this will go on before we try to solve the problem rather than just pull
models from shelves one-by-one.

Lithium-ion batteries pack a lot of power in a small
package compared to nickel-cadmium, making the toys light enough to take
flight.  Yet, it seems obvious that Lithium-ion
technology and flying toys are somehow a bad combination, but why?  Some quick research uncovered these facts
about Lithium-ion batteries:

• Lithium-ion is fragile and
  requires a protection circuit to maintain safe operation.
• 
  The maximum charge and discharge current must
  be properly limited; overcharging is dangerous.
• 
  The battery will become more vulnerable to
  failure if subjected to impact, crush or high rate charging.
• 
  Lithium-ion Polymer, generally thought of as
  safer and more stable, is often compromised in commercial use to improve conductivity.

So let us get this straight.  We are putting fragile chemical cells that
are only safe if charged perfectly and not subjected to impact into products
that are used by children and flown into walls by design.  One manufacture even places a sticker on the
package touting that the helicopter “Won’t harm walls.”  Unless, of course, it catches on fire.

ASTM F963-07, the Standard Consumer Safety
Specification for Toy Safety, is silent on battery usage for motorized aircraft
and vehicle toys, but this may soon change. 
Buried on the CPSC website is a document created September 8, 2008, titled:
CPSC Staff Draft Recommendations for Inclusion in ASTM 963-07,Safety Specification for Toy
Safety, to Address Incidents with Rechargeable Battery Powered Toys. Staff recommendations
include certification requirements for both batteries and chargers, battery
charge and overcharge tests, short circuit protection tests and discharge
voltage requirements.

While I commend the CPSC for
addressing the issue, the question remains as to whether such additions to the safety
standard will actually solve the problem in the case of toys like flying, or
rather, crashing helicopters.  The certifications
and tests will help assure that batteries and chargers are in good condition
when they leave the manufacturer, but what about after the eighteenth time
my son tries (and fails) to do a triple, loop-de-loop, sideways, tunneling soar-about
his bunk bed?  Can less than a half inch
of styrofoam protect such a fragile battery during a 10-year-old’s air
show? 

The new CPSC recommendations suggest
that batteries in toys comply with ANSI C18.2M, the safety standard for Portable
Rechargeable Cells and Batteries developed by the National Electrical
Manufacturers Association (NEMA).  The standard’s purpose is “to ensure [batteries’] safe operation under a variety of user and environmental conditions.”  However, until those test-conditions include
flying a Lithium–ion battery twenty-five feet into the air, clipping it against
a Magnolia branch, then smashing it into the driveway a few dozen times, flying
copters at our house will remain grounded.

Some of the recalled helicopters and airplanes are pictured here.  A more complete list of 2006-2008 recalls follows.

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