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دوشنبه 9 اردیبهشت 1392 :: نویسنده : علیرضا عبداللهی

The Truth and Fiction About Batteries



Truth and Fiction About Batteries

Batteries have also been in the news -- Boeing's new 787 Dreamliner has been under fire for using batteries that were…well, on fire. Such incidents underscore battery limitations, though there are few black-and-white truths about battery behavior, according to Isidor Buchmann, founder and CEO of Cadex Electronics and author of “Batteries in a Portable World.”

The Truth and Fiction About Batteries

Truth and Fiction About Batteries

Batteries have also been in the news -- Boeing's new 787 Dreamliner has been under fire for using batteries that were…well, on fire. Such incidents underscore battery limitations, though there are few black-and-white truths about battery behavior, according to Isidor Buchmann, founder and CEO of Cadex Electronics and author of “Batteries in a Portable World.”

So, what is going on in that battery of yours?

Under the Hood

All batteries use a chemical reactions to generate current. For example, the dry cell in a smoke detector or TV remote relies on a reaction between manganese dioxide, zinc, and ammonium chloride. Potassium hydroxide plays a role in alkaline batteries, while you'll find zinc chloride in so-called "heavy-duty" batteries.

Despite the name, heavy-duty batteries aren't superior to alkaline cells, which typically last more than twice as long, according to manufacturer Rayovac. In fact, one tip sometimes seen on Internet forums is true: After using an alkaline in a device like a digital camera that puts a heavy load on the battery, it still has plenty of life to give in a low-drain device that requires a heavy-duty cell.

“Alkaline increases resistance with usage,” Buchmann said. “You can continue using them in a kitchen clock when they come out of the digital camera.”

Battery Safety

With occasional reports about battery fires and explosions, some people fear that rechargeable batteries are unsafe.

Although nickel-metal-hydride (NiMH) and nickel-cadmium (NiCd) rechargeable batteries are still in limited use, most modern rechargeable devices use lithium-ion technology. And when you see news stories about burned phones, laptops and airplanes, it's usually lithium-ion batteries which are to blame. So are lithium-ion batteries really fire-prone?

Hirohito Teraoka, director of Technical Marketing for FDK Twicell, says such fires are rare. He also says that the solid-state lithium-ion polymer batteries in your home devices are safer than the liquid lithium-ion cells in the 787 Dreamliner.

“The electrolyte inside [a commercial] lithium-ion battery is in liquid form and is flammable, causing a risk if external or internal short circuits occur,” Teraoka said. “[Consumer-grade] solid-state rechargeable lithium batteries are considered safer than commercial lithium-ion batteries.” To protect against sudden heat increases, or thermal runaway, these batteries include safety features such as circuit interrupts, electronic "fuses," and vents that allow gases to escape before they can burst into flame.

Battery Memory

Have you heard stories about rechargeable battery "memory effect"? In a nutshell: If you don't fully discharge your battery before recharging it, the battery will only "remember" part of its capacity, and the run time will suffer.

This myth does have a basis in fact. NiCd batteries, when discharged repeatedly to the same level before recharging, eventually lose their full capacity. Fortunately, NiCd batteries are rarely -- if ever -- used in consumer devices anymore, and so your Samsumg Galaxy is immune to this ailment.

“Memory is only present in nickel-based batteries,” Buchmann said.

On the other hand, it’s true that your laptop’s battery periodically needs calibration with a full discharge/recharge cycle to get the best performance. Buchmann said engineers call this effect "digital memory." Unlike the memory effect in NiCd batteries, this doesn’t hurt the battery's actual ability to charge. Instead, it might just keep your device from using all the capacity available until it's re-calibrated.

Battery chargers themselves can be another source of confusion.

Consider electric cars, for example. High-quality modern chargers are "intelligent," charging quickly at first, then slowing and stopping as necessary. However, Teraoka said high-powered quick-charge stations might reduce the useful life of an electric vehicle's battery since it can defeat the lithium-ion battery’s protection circuits. But not everyone agrees: Manufacturers like Mitsubishi claim that drivers can fast-charge regularly without significant issues.

Refrigeration and Recycling

You might know the old "helpful hint" of storing batteries in a refrigerator to extend their life. It turns out that this might not be so helpful after all. Energizer claims refrigeration won't preserve a charge much better than storage at room temperature, and the icebox's condensation can corrode a battery, ending its life before its time. Buchmann concurs.

“The effect is moderate,” he said. Buchmann further says that keeping batteries above 86 degrees Fahrenheit can hasten aging.

On the other hand, what you've heard about recycling batteries is true: Materials in almost every type of battery -- especially rechargeables -- are an environmental concern.

Certain types of rechargeable batteries might contain heavy metals such as cadmium, lead and lithium, according to Jennifer Childress, director of marketing at nonprofit Call2Recycle.

How about household dry cells? Since 1996, when federal law eliminated mercury in single-use batteries, Childress says most communities consider alkaline batteries and their kin to be disposable in normal household waste.

Keeping Your Batteries Alive

Modern batteries are larger and more efficient, but using all the bells and whistles on a mobile device can still deplete its energy in short order. Here are some best practices to maximize your battery's life:

A digital screen is the largest drain on a device's battery. Turn down the brightness as far as you feel comfortable with and set the screen sleep interval to its shortest setting.

Limit or close your background apps and disable "push" updates. Allowing your calendar and email to update every five minutes can drain your phone even when you're not using it.

Disable the receivers or transmitters you aren't using. If you're not in a hotspot or using a wireless headset, turn off your Wi-Fi and Bluetooth.

Use your device's "power saver" mode, which includes the manufacturer's optimum settings for preserving battery life.

Turn off your phone or use its "Airplane Mode" if you'll be spending time in an area without a strong cell signal. Phones will keep searching for a signal even when asleep, consuming valuable power.







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