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12/01/2004
Battery Blowups
On Thanksgiving, my wife and I were taken out for dinner by our
generous editor, Brian Trumbore. That morning, without the
usual chores accompanying Thanksgiving dinner at our house, I
began a project that I’ve been putting off for decades. I got out
my camcorder to make a photographic inventory of the contents
of our home, something every homeowner should have to back
up any insurance claims in case of fire.
Before starting the project, I had to charge the camcorder battery.
I was surprised to read in the instructions that, if I didn’t plan to
use the camcorder for a prolonged period of time, it was best not
to store the battery in its fully charged state. It was then that I
realized I had a lithium-ion battery, not the nickel-cadmium
battery I had thought it to be. Coincidentally, a day or two
before Thanksgiving, I saw an AP article by Elizabeth Wolfe in
the Star Ledger on exploding cell phones, the culprit being the
lithium-ion batteries in these phones.
Having spent 17 years at Bell Labs working on lithium batteries,
I was not totally surprised to read that there were 83 cases of
exploding or fiery cell phones during the past two years.
Considering the roughly 170 million cell phone users in this
country, 83 such incidents is statistically a relatively low number.
I wouldn’t be surprised if there were more than that number of
incidents involving jump-starting cars with dead lead-acid
batteries. However, only a handful of cell phone fires or
explosions bankrupted a Canadian company that was the first to
market lithium (not lithium-ion) batteries for cell phones in Japan
back in the mid-1980s. And 13-year-old Michael Sathre of
Oceanside, California wouldn’t be impressed by the low
probability of an exploding cell phone. One of the recent
victims, he was holding a cell phone when it blew up, bloodying
his hand and fragments of the phone hit him between the eyes;
fortunately, not in the eyes.
We’ve discussed lithium-ion batteries before but, in light of these
explosions and fires, let’s review how lithium-ion batteries have
to be treated more kindly than other more common batteries.
First and foremost, the batteries and the cell phone must be
matched in one very important respect. It is absolutely required
that there be a circuit of some kind that prevents charging of the
battery above a certain voltage. If the battery contains more than
one cell, each cell has to be protected from exceeding a certain
voltage. Generally, each cell will contain a miniature circuit
with a silicon chip that limits the voltage of the cell. It’s also
possible that the voltage-limiting circuit is incorporated in the
cell phone itself.
Invariably, when you buy a cell phone, the battery comes
installed in the phone. Sometimes, the manufacturer of the
phone will also be the manufacturer of the battery. I don’t know
the figures these days but a substantial number of cell phones
come with batteries made by a different manufacturer. Either
way, you just have to trust that your cell phone/battery
combination is a good one if you buy a reputable brand.
When replacing a battery, however, it’s up to you to buy a
suitable replacement. I personally would forego looking for any
discounts or shopping some unknown online source. According
to U. S. cell phone manufacturers, most of the explosions and
fires are caused by “counterfeit” batteries. You definitely don’t
want to be like those who buy the purported Gucci bags or Rolex
watches from street vendors in Manhattan! Never buy any
replacement batteries that are not the specific type and model
number(s) prescribed in the cell phone manual.
Even reputable cell phone companies can have problems with
battery manufacturers, as illustrated by the fact that in June
Verizon recalled around 50,000 batteries used in one cell phone
model. The Japanese company Kyocera has recalled over a
million batteries this year in two separate recalls and has not only
changed vendors but has doubled its own internal testing of
batteries.
There are some things you can do to help prevent problems with
lithium-ion batteries. High temperatures aren’t good for any
battery. Leaving a cell phone in your car in the summertime can
subject the battery to temperatures of 140 degrees Fahrenheit or
even higher in the desert country of our Southwest. Too high a
temperature and you can initiate “thermal runaway”, a condition
in which the temperature in the battery keeps increasing until the
battery blows or vents and catches fire. (I just took out the
lithium-ion battery in an old Motorola cell phone and it had a
warning not to use over 60 C, which is 140 F.)
High temperatures can also arise during normal operation if the
heating vents in the cell phone are blocked. You now have cell
phones that double as cameras and computers. Packing all these
functions into one small package means more power and more
heat is generated. Block the vent or design in insufficient
venting and thermal runaway is a possibility.
Of course, there are other precautions you should take with
lithium-ion and most other batteries. For example, don’t short a
battery by having it come in contact with metal keys, coins or the
like. Don’t drop, crush, take apart or otherwise manhandle any
battery, especially if it’s charged. Don’t try to dispose of one in
a fire! Never, never substitute one kind of battery for another
and never try to charge a battery with a charger not specifically
designed for that particular model and type of battery.
Oh, I did finish at least a fair approximation to an inventory on
Thanksgiving and the tape is now in our safe deposit box. For
my wife and me, Thanksgiving was especially pleasant. She
didn’t have to cook and I didn’t have to wash the dishes! We
also had the unexpected pleasure of meeting a loyal reader of
these columns, a delightful young lady. I hadn’t realized that she
had contacted Bortrum asking if he could suggest a science
project for one of her children in school. I e-mailed her a
suggestion for a crystal growth experiment. Apparently, the
project worked out well and her child won an award. Hearing
that made Thanksgiving even more pleasant.
Allen F. Bortrum
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