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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