A Device That Charges a Smartphone by Dropping a Weight

I have never met a person who was satisfied by their smartphone’s battery life, and many of us can’t even get through a single day without having to charge up our phones. If every person living in the United States fully drained and recharged an iPhone every single day, we would consume a total of about 654,000,000 kWh of electricity every single year — costing about $80 million dollars. In reality, that’s only about $0.25 a year for each person, but it’d still be nice to save some energy. Fortunately, Tom Stanton’s DIY gravity-powered smartphone charger can work without touching the power grid.

Alright, to be frank, there is nothing practical about this project, despite me throwing scarily big-sounding statistics at you. But it is a fun exploration of alternative means of generating electricity. His system is designed to be mounted somewhere high up, and generates electricity when a weight is dropped from that height. Is has a standard USB-A port that is compatible with virtually every smartphone charger ever made. Depending on the height the device is placed at, the mass of the weight, and your phone itself, this could charge your phone in something like a few hours — assuming you dropped the weight over and over again repeatedly for that entire time period.

Stanton's device works almost exactly like one of those hand-cranked emergency flashlights. But instead of turning the crank by hand, the internal generator is spun by the cable attached to the falling weight. A generator is essentially just an inverted motor, though there are usually differences designed to optimize them for the task. In this case, Stanton geared up the mechanism so that one turn of the “crank” equals many turns of the generator. That requires more weight to be dropped in order for it to turn, but means that the weight needs to be dropped a fewer number of times to generate an otherwise equal amount of energy. A solar panel or actual hand-crank generator are far more useful, but this project does a good job of demonstrating how potential energy can be converted into electricity.