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Taking apart the iPhone 6 Plus battery

Posted: 15 Jun 2015 ?? ?Print Version ?Bookmark and Share

Keywords:lithium-polymer? batteries? smartphone? iPhone 6 Plus? Apple?

Taking a closer look at Apple's iPhone 6 battery helps identify the one variable that defines manufacturing cost. Li-polymer batteries are everywhere: cellphones, tablets, laptops and hybrid or electric cars. We rarely think about them except when the discussion turns to the rather short battery life seen in some consumer electronics. Smartwatches, like some laptops, come to mind where battery life is measured at less than a day. This has me thinking about batteries, and are there commonalities between the batteries seen in smartwatches, cellphones and tablets.

And this has our curiosity piqued at TechInsights as to whether a single variable can be used to predict their manufacturing cost (bill of materials or BoM)? Simple proxies would include the battery mass or its charge capacity as both are easily measured.

The image shows a typical lithium-polymer pouch-type battery taken from a smartphone, in this case the Apple iPhone 6 Plus. The copper anode and aluminum cathode current collector tabs are seen extending out of the right end of the battery package. A flex ribbon containing control electronics has been removed from this battery but is shown on another iPhone 6 Plus battery in the next image. We note the use of two Ricoh battery protection IC's and a Texas Instruments Li-ion fuel gauge.

Apple iPhone 6 Plus Li-polymer battery

Apple iPhone 6 Plus Li-polymer battery. (Source: TechInsights)

iPhone 6 battery electronics

iPhone 6 battery electronics. (Source: Deep Dive Teardown of the Apple iPhone 6 Plus A1524, TechInsights)

Our first question: is this battery special? And to answer this we examine the energy density (Wh/g) for a number of batteries used in smartphones, cellphones and tablets that have passed through TechInsights labs over the last year or so.

The graph shown below includes smartwatch batteries that tend to be less than 25g, cellphones of various kinds, and tablets weighing in at more than 70g. The slope of the straight line through the data is about 220Wh/kg and it is a pretty good fit to most of the data points. The small scatter in the data points about the fitted line indicates that these batteries are using the same or at least fairly similar cell technologies. A significantly improved battery should lie well above the trend line, and a poor battery technology would be below the trend line. A few batteries are measurably below the trend line, though this underperformance might be due to excess packaging that would increase the weight of the battery without adding capacity.

Li-polymer battery capacity

Li-polymer battery capacity. (Source: TechInsights)


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