The iPad's most revolutionary feature isn't the 2048x1536 Retina display LCD panel, or the 4G LTE connectivity. It's something that you can't see.

It's the battery.

Apple's put a lot of cool, but power-hungry technology into the new iPad. That Retina display screen, the quad-core graphics processor and the LTE modem all put pressure on the battery, yet Apple has managed to keep the iPad's battery life at 10 hours.

How has Apple managed this?

While Apple has undoubted put more power efficient technology into its next-generation iPad --- for example, dropping the processor architecture down from 40nm to 28 nm would have resulted in quite a significant power saving --- the more dramatic improvement has been the battery itself.

Between the release of the iPad 2 last year and the announcement of the new iPad yesterday, Apple has nearly doubled the capacity of the battery, taking it from 25Wh to a massive 42Wh. Measured in milliamps this boosts the battery from 6944 mAh to a monstrous 11,666 mAh.

And it's clear that Apple had no choice if it wanted the new iPad to be the device that it is. Even with this massive bump in battery capacity, the device is still only rated as having a 10-hour battery life. Without this boost to the battery, the old power cells would have been lucky to keep the new iPad going for 6 hours. It's clear that Apple isn't interested in getting into a numbers war over battery life, but instead wants to add new features incrementally while keeping battery life at that 10-hour mark.

The obvious way to boost the battery's capacity would be to double the battery size, but given that the new iPad is only fractionally thicker and heavier than the iPad 2, it's highly unlikely that the battery is significantly bigger than the one in the iPad 2.

There's another issue with adding a bigger battery, and it's all down to weight distribution. You might not have noticed by the weight of the iPad is perfectly balanced in order to make holding the tablet as comfortable as possible.

Big battery cells not only add weight, but also require careful engineering to make sure they don't unbalance the device. Keeping the cells as small as possible and in the center of the device makes engineering the rest of the device easier.

All this points to something very significant. It suggests that Apple has managed to increase significantly the power density of the Li-ion cells that it uses. In an industry that has seemed stagnant for some time now, this is quite an achievement and goes to show that Apple's battery research labs and manufacturing plants have been hard at work. There's no doubt that we're going to be seeing the fruits of this labor in other Apple products soon.

However, Apple has pulled off this huge increase in battery capacity (I'm looking forward to the teardowns of the new iPad), it undoubtedly changes everything... again.

Image source: Apple.

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