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Today, most of us have an array of portable computing, communications and infotainment devices that depend on batteries -- laptops, mobile phones, radios and music players to name a few. Understanding a little about modern batteries can make life easier, particularly about the rechargeable batteries used in computing devices like laptops.
Yesterday and today
Alessandro Volta is generally credited with inventing the primary cell (non-rechargeable) chemical battery, around 1800. Gaston Planté gets credit for inventing the first "secondary cell" (rechargeable) battery, in 1859, based on a lead-acid chemistry that is still used today.
The nickel-metal-hydride (Ni-MH) and lithium-ion (Li-Ion) rechargeable batteries that are now commonly used in portable devices have been commercially available only since the early 1990s. Before that, rechargeable batteries were of the nickel-cadmium (Ni-Cad) type. For a comparison of the strengths and weaknesses of each battery type, click here.
Today's laptop and cell phone batteries are primarily of the Li-Ion type. Li-Ion batteries have been in the news -- you may have seen pictures in the newspaper of a burning laptop at a Tokyo conference, or of a charred pickup truck whose interior succumbed to a flaming laptop (which also ignited some handgun ammunition stored in the glove compartment). Apple, Dell, Fujitsu, Lenovo and Sony are among the manufacturers that have announced recalls of several million Li-Ion laptop batteries to deal with potential fire risks.
What do you need to know?
We recommend you avoid storing your laptop near your ammunition, and not just because of battery issues. Here are some other suggestions:
- If you have a battery that is subject to a recall, take it out and run your laptop on A/C power only until the new battery arrives. The risk of fire is usually exceedingly small, but there's no sense in taking any chances.
- Batteries generate heat when producing power, and so do the powerful microprocessors that make today's laptops so productive. That's why laptops have vents and tiny cooling fans. Don't block the vents with papers, clothing, etc. (Males in particular may want to consider other risks associated with laptop heat.)
- Batteries don't generate heat when they're not producing power. If you want to reduce your fire risk to zero, don't leave the device on when you're not using it. (We realize you can't follow that advice for devices like your phone, but you can certainly turn your laptop off when you're not going to use it for while).
- Li-Ion batteries don't suffer from the same "memory" effects as the rechargeable Ni-Cad batteries of old, which needed full discharges regularly. (Ni-MH don't suffer from the same magnitude of memory problems either.) But there are still memory issues to consider. Your laptop's Li-Ion battery needs to run down at least a little every once in a while, otherwise it may be unable to hold a charge. In other words, don't keep it on A/C power all the time.
- On the other hand, it's generally recommended that you avoid frequent full discharges of a Li-Ion battery. Lots of moderate charges are the ideal. You may find you need to let the battery run down to the minimum every few months, however, to keep the "battery meter" accurate.
- If you store your laptop for an extended period, the current recommendation is to leave it with a partial battery charge (about 40-50%). You should also store it in a cool place (about 15°C / 59°F is ideal). Remember that even in the best of circumstances, the battery will probably lose 5-10% of its charge every month.
- Batteries don't like temperature extremes -- and neither, generally, do the devices they power. High heat is particularly to be avoided. (This is another reason why cars are not the ideal place to store a laptop, particularly in Florida.)
- Nothing lasts forever. Li-Ion batteries are typically rated for several hundred charge-discharge cycles (300-500) and 2-3 years of productive life. After that, even with perfect care, you'll probably need a new one unless you want to remain tethered to an A/C outlet. The good news is that battery technology improves all the time. So each new laptop battery you get will last longer than its predecessor.
- While Li-Ion batteries are not as toxic to the environment as some other types, they still shouldn't just be dumped like any other trash. It's better for the environment to keep them out of the solid waste stream and it'll save resources too. You can find a battery drop-off location near you at this site.
Battery University (Cadex Electronics)
Excellent brief, down-to-earth content on just about everything you could possibly want to know about batteries.
Battery types (Wikipedia)
Links to materials on battery materials, sizes, history, etc.