8. Explosions and Conclusions

Why The Explosions?

Bottom line, the explosions are caused by a short circuit inside a battery cell. Sony admitted to metallic contamination of the Lithium-ion chemicals. If metallic impurities (such as random particles of metal) get inside a battery cell, chances are that nothing will ever happen. However, there is a very, very small chance that - with movement of the battery or the equipment it is powering - these particles could fall into a configuration that short circuits the cell. In fact, it might only occur with a handful of batteries in a million. That looks a lot like 0% probability if you round it down. But it did happen and some cells did short out and, essentially, melted down.

If you connect the + and the - sides of an unprotected Lithium-ion cell on the outside of the battery, you better get far away, and fast. Luckily, the internal protective circuitry between the + and the - terminals normally prevents such a short from occuring. In the case of the cells Sony recalled, however, the + and - ends became connected together inside the cell and then, with the protective circuitry unable to function, Boom!

Batteries Now And In The Future

Most major brand batteries come out of Japan, with a good chunk coming out of the Sony Energytec division. The good reason for this is Sony is on the cutting edge of battery tech. As we've seen, Sony goes through some lengths to engineer safety into the batteries, but it is not possible to make them 100% safe. Until recently, most battery explosions have been attributed to off-brand Chinese batteries without significant protective circuitry or manufacturing safeguards. Now we know that even a brand name battery is susceptible to problems.

What does the future hold for battery technology? A lot of hope is being held out for fuel cell batteries. Essentially, this technology allows an energy dense fluid or gel similar to gasoline to be put into a tank in your mobile gadget. Now, alcohols and other hydrocarbon fluids tend to have quite high energy densities, and in lieu of the kind of dangers we're experiencing today with high energy density battery packs - let's just wait and see before we start pouring flammable substances into our gadgets!

Ten Lessons Learned

Keeping your notebook battery cool can extend its life dramatically. Notebooks that have a "rapid charge" feature will wear out the battery pack faster. Putting your battery through frequent charge and recharge cycles often will wear it out faster. Compare one battery to another battery using Watt-hours (voltage x mAh / 1000). Don't bother opening up your battery pack unless you have a good reason! Li-ion isn't 100% safe, but chances are, an explosion won't happen to you. NiMH batteries are pretty safe but have lower capacities. Li-ion batteries last 12-18 months thanks to hot notebooks. NiMH battery life is typically rated by cycles (300 discharge and charges). Your dull looking notebook battery is a riot of colors on the inside!

Calvin Chu holds a degree in Computer Engineering from the University of Michigan.

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