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What do the iPhone, Motorola Droid Razr Maxx, and Nokia Lumia 900 have in common? The fact that their batteries can't easily be removed.

Last week, the Motorola Droid Razr Maxx wowed us with its slim physique and a long battery life that nearly doubled that of the original Droid Razr. The one component that made it possible is the unremovable--or embedded--battery.

Cell phones with batteries you can't pop out are more common than you may think. Apple has made embedded batteries a mainstay in every iPhone since its first.

In fact, add up the iPhones, both Droid Razrs, two Nokia Lumias (800 and 900), and the upcoming Motorola Droid 4 and it appears we have a trend on our hands.

More than just looks What's the advantage of a battery you can't take out? Aesthetics are one obvious reason to go that route, with designers opting for a fluid, unibody motif.

Take, for instance, the Nokia Lumia 800 and forthcoming 900. When asked why the company chose to embed the battery, Jerry Hart, Nokia's senior product manager of Windows Phone, told CNET, "We have striven to deliver a beautifully crafted device, created from a single piece of polycarbonate with precision machined details."

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Hart added that the unibody design made possible by the embedded battery makes the phone "seamless," "extremely rigid," and "free from split lines that disrupt the feel in hand and the visual purity of the design."

Slimness is absolutely part of the equation, since phones without the small grooves, nooks, and air pockets needed to make it so you can open a back cover and pull out a battery have the potential to be thinner.

In fact, when you don't have to design a product around popping out its battery, you have far more options. Engineers can use batteries in shapes, sizes, and configurations that deliver the requisite charge but are impractical to remove. That, in turn, can allow the industrial designer to create phones with creative contours.

Motorola certainly agrees. Manipulating the smartphone's shape and size was its great goal and accomplishment with the Droid Razr; its superskinny superphone measures less than 0.3 inch thick.

The Droid Razr Maxx delivers the second message that ultraslim phone bodies can play a practical role as well. At less than 0.4 inch thick, the sequel offers nearly double the battery capacity, at a thickness that's still slimmer than the 0.5-inch status quo.

Phone Battery capacity



Rated talk time



Depth



iPhone 4S

1,430mAh 8 hours 0.37-inch Motorola Droid Razr

1,780mAh 12.5 hours 0.28-inch Moto Droid Razr Maxx

3,300mAh 21.5 hours 0.35-inch

Nokia Lumia 800

1,450mAh 13 hours 0.47-inch

Nokia Lumia 900

1,830mAh 7 hours 0.45-inch



*Battery size isn't the only indicator of slimness or performance.

Embedded batteries are also harder to lose and less likely to sustain damage, since there's usually no door to pop off when you drop the phone. More than that, sealing the back cover means you're protecting the internals from the elements, which could make the phone more rugged.

Nokia's Hart agrees. "There is no extra air inside the product," he told CNET in an e-mail. "The result is that the Nokia Lumia 900 is as strong and efficient as it is beautiful."

The big 'but'

There's at least one main point of contention that comes up again and again: what happens when the battery goes kaput?

When phones go on the fritz, as they do, one common solution when rebooting fails is to remove the battery, sit a minute, and put it back in. In extreme cases when the battery weakens or dies, people can extend a phone's lifespan by swapping in a new battery they bought online or elsewhere. With an embedded battery, neither course is an option.

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Not that Apple, Motorola, and Nokia don't have their own fixes. Holding down the power button for several seconds performs a hard reset for the phones. Nokia shares that it has built in a procedure to reset the phone to factory settings if worst comes to worst.

Then there's Apple, which has its retail stores to offer on-site support for Apple products, a situation that extends customers a certain safety net closer to home.

Without the same option for Motorola and Nokia phones, owners would need to lean more heavily on the carriers and manufacturers to fix or replace handsets with defunct batteries. In some cases that could leave the user without a phone for days or even weeks.

We need a fix-it promise

Based on the release of the Lumias and Droid Razrs, it certainly looks like a class of superphone could emerge that uses embedded batteries to achieve a knockout design.

Sarah Tew/CNET

I, for one, am anxious to see phone makers break out of the boring black box and let designers create radical silhouettes. If embedding the battery is the way to do it, so be it.

As for those concerns about dealing with a dying embedded battery: they're valid. But then again, how often does the average phone owner actually tinker with the battery on a monthly basis?

Although some people tote around spare batteries, I do think we'll start seeing more people consciously take a shine to phones with embedded batteries when manufacturers do two things: First, provide these smartphones with strong, long-lasting tickers like the Droid Razr Maxx has that can process a gargantuan number of multimedia tasks (like streaming movies) over at least two years, the average lifespan of a carrier contract.

Second, phone makers will need to establish a clear company process for helping customers who do run into problems, and minimize the length of time that people are separated from their phones.