As you can see, the main danger is from toxic fumes. Even so,
standard fire extinguishers including lots of water can be used.
The electrolytes in the cells start to break down between 160 and
230 degrees Fahrenheit. The release of gasses from the
electrolyte is what puffs the cells. As long as thermal runaway
doesn’t start, the battery may still be safe. However, it’s time to
put it in a safe place away from flammable objects and watch it
for up to 30 minutes. If the battery appears stable it can be
cautiously recharged and
reused. The battery will
probably not be as “good” as it
was before it puffed. However,
even less expensive packs are
getting better and more able to
stand abuse every year.
Today’s inexpensive packs are
better than the top quality ones
being charged in the 2008
picture below. None the less,
good chargers made charging
even 42 - 6S packs a safe
procedure. Kevlar pants aren’t
needed.
PROPWASH
April 2013
13
Lipo Safety Revisited
By Lohring Miller
NAMBA Safety Chairman
I first wrote about lithium polymer battery safety in 2007.
The batteries were new to boaters and there were many wild
stories about how unsafe they were. I tried to dispel those fears
as well as provide a lot of factual information about the
batteries and the power available. The basics haven’t changed
despite great improvements in the available power as well as
battery safety. They store increasing amounts of energy and
need to be handled with respect. However, as the recent fire at
the 2012 NAMBA Electric Nationals shows, there still can be
problems. To put this in perspective, though, I have personally
put out two gasoline fires in model boats as well as seen 3
cases of badly cut fingers from props. I have seriously abused
electric power systems in full size and model boats. I have
puffed batteries, melted motors, and exploded (really) speed
controls. I have never seen a lipo fire. Lipos are much tougher
than lead acid batteries under the same charge and discharge
conditions. Modern balancing chargers and low voltage cut off
speed controls can prevent lipo problems if these aren’t
overridden.
As far as I can find out from the people involved, a 6 cell
battery pack that had been abused in an offshore race was not
charging. The charger’s safety check was bypassed by not
connecting the balancer. As a result one cell was badly
overcharged, and thermal runaway occurred starting a fire.
The fire was quickly beat down with a conventional
extinguisher, the battery was pushed into a metal pan and
dumped into a cooler full of water. The damage was limited
and no impossible to extinguish metal fires or explosive
reactions with water happened.
From http://www.mpoweruk.com/lithium_failures.htm
“The Lithium content is combined into other compounds
which do not react with water. The amount of Lithium
deposited during the Lithium plating when cells are damaged
as described above is very small and not usually responsible
for the fires which have occurred. Furthermore, many of the
reported fires are due to burning electrolyte rather than the
Lithium compounds.”
From Venom’s MSDS:
Extinguishing Media:
CO2, Dry chemicals, water or Foam
Extinguishers Fire-Fighting Procedures
: Use a positive
pressure self-contained breathing apparatus if batteries are
involved in a fire. Full protective clothing is necessary. During
water application, caution is advised as burning pieces of
flammable particles may be ejected from the fire.
Toxic gases (HF, PF6) will be formed if cells or battery are
involved in a fire. Cells or battery may flame or leak
potentially hazardous organic vapors if exposed to excessive
heat, fire or over-voltage conditions. Damaged or opened cells
or batteries may result in rapid heat and the release of
flammable vapors. Vapors may be heavier than air and may
travel along the ground or be moved by ventilation to an
ignition source and flash back.
“Propeller’s by Chris Hoffmann”
Complete Propeller Service
Sharpening, Balancing, and Modifying
All Props in Stock!
ABC — PropShop — Octura
ABC and PropShop Dealer
Nine Time NAMBA SAW Record Holder
www.dasboata.com
Contact Chris at
dasboata@aol.com
Model boater Mike Bontoft
monitors the Lipo charging
station