viernes, 26 de noviembre de 2010

¿Porque la baterías recargables “mueren”?

Excelente artículo que explica porqué las pilas y baterías recargables tienen una vida útil, y que hacer para prolongar su funcionalidad al máximo.

Giz Explains: Why Batteries Die

Inside almost every gadget lurks a ticking time bomb. In two years, or maybe three or four, it will die, rendering your gadget useless. Possibly permanently. So, what are these awful little bastards? They're called batteries.

The concept of battery death is ingrained in any gadget buyer's psyche, whether he knows it or not. Just as a computer's software always seems to slow down, or a phone mysteriously accumulates scratches, batteries' slow creep toward uselessness is simply a part of the fraught relationship between gadgets and time. But who, or what, is to blame? Of course, the companies that make and sell these batteries are somewhat guilty, but you know what? So are we.

How Rechargeable Batteries Work

When we talk about rechargeable batteries in gadgets, we almost always mean lithium ion batteries, or something very similar.

In short, the lithium ion batteries work like this: A positive electrode (cathode), made of non-metallic lithium, is connected to a negative electrode (anode), made of carbon. To charge a battery is to repel ions (electrically charged atoms) of from the lithium cathode over to the carbon anode, where they deposit themselves. The release of these ions later—or more specifically, the current caused by their flow back to the lithium cathode—is where your laptop or cellphone gets its power from.

At its heart, this is a chemical process; charging and discharging are both chemical reactions, and the passage of ions from cathode to anode, or vice-versa, represents a fundamental change in the makeup of each.

Virtually every other kind of battery works on these same physical principles; lithium ion batteries are just some of the best suited for use in consumer electronics. They're light, compact, hold a hell of a charge, and most importantly, can be charged hundreds of times before deteriorating significantly. They have long lives. But not unlimited ones.

Why They Die

Battery death starts the second they leave the factory. It's unavoidable and irreversible, and in lithium ion batteries, can totally destroy even a rarely used, mildly charged battery in as little as a few years. With

Saving your battery
Those of us stuck with the slowly expiring batteries of today will have to help ourselves. Luckily, there's quite a bitwe can do. Lithium ion batteries degrade much more quickly when hot, so keeping a laptop ventilated is vital. (This is as easy as not using a pillow as a laptop table, or placing a bit of folded paper under the rear of the laptop's base to enhance air flow.)

Rechargable batteries also die more quickly if they're left fully charged, so instead of keeping a laptop plugged in all the time, let it rest a bit, or plug/unplug it through a workday. Accordingly, phone batteries tend to last longer than laptop batteries simply because of how people charge and de-charge them. For the stunning correlation between heat, charge level and battery life, see Battery University's article here.

constant use (and abuse), a lithium ion's lifespan can be under two years-less—if losing more than a third of its capacity counts as death. Knowing that batteries work using a chemical process, it's reasonable to expect some degradation. After all, no chemical reaction is perfect, and all result in some kind of energy loss, often producing unwanted results or substances. Batteries are no different.

"As batteries age, obstacles arise that reduce ion flow, and eventually make them unusable," says Isidor Buchman, President of battery diagnostics and analysis companyCadex. "There are certain buildups that occur on the electrodes that inhibit ion flow," he says. This results in a steady decline in performance.

What he's talking about, mostly, is the gradual degradation of the cathode—the lithium part—by means of slow, unavoidable chemical changes. Repeated subtraction and addition of ions actually alters the structure of the lithium material, making it less receptive to future exchanges—a bit like a rag that's been soaked and wrung a few hundred times too many. It becomes threadbare, molecularly speaking.

Giz Explains: Why Batteries Die

More destructively, the repeated and constant chemical reactions inside the battery leave dissolved metal on the cathode and, to a lesser extent, the anode. This can eventually form a sort of unwanted metallic plating on both.

Additionally, electrolytes in the battery are prone to decomposing. They oxidize on the cathode, leaving something like rust blocking the way of ions that are trying to jump back and forth. Common shorthand for this phenomenon is corrosion, and its effects are profound: The resulting battery, with its tired electrodes, broken-down electrolytes and corroded surfaces, is the picture of aging. It's now terrible at being a battery.

Buchman says that this process in an inherent part of current battery technology, but that it doesn't have to be so bad. ""The consumer doesn't want to pay much. [Batteries have] to be cheap. And they have to run for a long time; in a cellphone or laptop, run time is important." It's our demands and habits, he claims, that essentially give gadget and battery makers permission to sell us batteries with such close expiration dates. "Consumers don't want to pay more, don't want a bigger battery to carry, and demand a higher run time." The trade-off for a cheap, small, long-running battery: one that corrodes easily.

On top of that, the natural lifespan of some of our most valued electronics is extremely and artificially short. People get new phones every two years because their contracts are structured as such. Laptop specs become obsolete (or really, "obsolete") at nearly the same rate.

Think of it this way: Your iPod from two years ago might still work, but you'd rather have the new one, right? Your first gen unibody MacBook is stil a nice computer, but you're tempted by the new 13" Air. There's a reason we don't talk about battery death all the time, despite its severity.

How Things Can Get Better

Time heals all, including battery technology. Buchman says that the practical limits of lithium ion batteries have nearly been reached, but that new technologies are on the horizon. "Most of the research has been focused on the cathode. The anode has traditionally been a carbon product, but some are working on perhaps adding silicon, to gain higher energy density." In English: battery makers are concocting a new brew in search of a better cell.

The development of electric cars has also been a boon to battery research. Unlike Apple or Dell, car companies can't ship a device that's useless after a few years, so significant money and time are being expended to develop batteries that are powerful, capacious, andlong-lived.

As for what Buchman sees as the root cause of the problem—consumer pressure—that could be healed, too. If cellphone contracts become longer, or just disappear, or if one spec race or another cools down, consumers may not be clamoring for a new set of gadgets every other season, and battery death will become a more pressing problem. Then, just as car manufacturers are scrambling for longer-lived battery right now, the consumer electronics industry may need to find their own.

Lithium-ion diagram courtesy of Varta Automotive

Send an email to John Herrman, the author of this post, at


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