Environmental sizing of smartphone batteries

Smartphone use has increased at a phenomenal pace worldwide. In 2011 more smartphones have been sold than desktop pc's, notebooks, netbooks and tablets together. The total worldwide smartphone sales reached 472 million units in 2011, and 149 million of them were sold in the fourth quarter of 2011. The smartphone is, like almost every other mobile device, powered by batteries, limited in size and therefore capacity, which makes energy management paramount. While global demand and use of mobile devices continuously expands, the energy density of smartphone batteries has grown at an insignificant rate, but the use period still decreases because of high loads and big screens. In this paper we have studied the power breakdown of five smartphones on sale in 2011. We have defined three different user profiles for "heavy", "moderate" and "light" users and we can state that theoretically it is sensible to re-size the battery based on the user profile. While keeping the user period acceptable we can decrease the battery capacity for moderate and light users with 25%, reducing the worldwide energy needed to product smartphone batteries with 2.1 to 3.4PJ per year. In practice the aging of the battery will result in a decreasing battery capacity over its life. When taking this into account most batteries comply with the moderate users and only a resizing strategy for the light users is sensible. This will account for only 20% of all users and can result in a worldwide decrease of energy needed for producing the smartphone batteries with 0.5 to 0.9PJ.