Why Some Batteries Burn And Others Don't
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Analogies aside, let's take a look at what the problem really is and help protect users from having a notebook PC go "flame on" in their laps. In the simplest sense, the batteries burst into flame for one simple reason—the electrolyte (lithium salt) is dissolved using a highly flammable solvent. Overheat the electrolyte and result is flames. Now the question is, how does that electrolyte get so hot? Simply put, a short circuit in the battery creates the heat. The recalled batteries may have a manufacturing defect that makes a short circuit a possibility, and that is what everyone is worried about. While the battery manufacturer (Sony) isn't giving specifics on what the exact defect is, there are several factors that contribute to whether or not a battery will short, such as if the battery cells are aligned in parallel or perpendicular order, and how close they are to other heat sources, such as the processor or power supply.
One of the quickest ways to gauge the risk is to take a look at the heat generated by a notebook computer. When the Test Center took a look at the latest batch of notebooks, it was worth noting that the Panasonic Toughbook CF-51 only had a battery surface temperature of 76 degrees, slightly above room temperature. The highest temperature seen was 86 degrees with the Hewlett-Packard Compaq NW8440. While that is only a 10 degree difference, the question becomes, "Which notebook do you want on your lap"?
Beyond temperature, there are a few safety tips that users should follow: First off, if you drop a battery, perhaps you should consider replacing it, just in case there is internal damage. What's more, heat is the enemy here. While none of us will put their laptop computers on a stove, how many of us have locked one in a closed car on a hot summer day? Other things to avoid are third-party chargers that are not specified for the particular unit— too many watts during charging can overheat the battery. Safety all comes down to common sense, so as long as you know what these batteries are susceptible to, you can avoid those situations.
