From 2007 to 2016, the iPhone’s battery grew from 1400 mAh in the first iPhone to 1960 mAh in the iPhone 7 (ignoring the new plus size iPhones). The energy density of lithium ion batteries grows at an exponential rate (5-8% a year), doubling every ten years, according to Tesla’s J.B. Straubel. The iPhone’s battery density growth is lagging this trend probably due to the continuous push for thinner phones.
Using Microsoft Excel’s exponential regression functionality, the following chart forecasts future iPhone battery sizes based on the available historical data, predicting that the small (non-plus) iPhone’s battery capacity will reach 5000 mAh around the year 2036:
Moving on to the more interesting new plus-sized iPhones, Excel cannot do an accurate automatic exponential regression due to the fact that there isn’t enough historical data available on the plus-sized iPhones. By examining the above chart and manually doing the regression using a second series, I found that Excel assumed an approximate rate of growth of 3.81%, and an approximate rate of growth of the rate of growth of 0.09%. Using these same rates on current iPhone Plus battery sizes, we get the following chart:
As it can be seen, around 2024 the iPhone Plus battery size reaches 4000 mAh, and around 2029 it reaches 5000 mAh. If the trend toward ever thinner phones slows, then the 5000 mAh smartphone battery might be achieved at an earlier date. I am hopeful that at least one large manufacturer is brave enough to bet on much larger batteries as a selling point, instead of following Apple’s lead in making things thinner and thinner.