Build Your Own Hand-Cranked Powerbank to Charge Your Phone in Emergencies

Cameron Coward
Nov 26, 2018 · 2 min read

Like most people, you probably rely very heavily on your smart phone. And we’ve all experienced the inconvenience of a dead phone battery, which is a hassle even when you’re just out running errands. However, that inconvenience can easily turn into a legitimately dangerous situation if your phone dies during an emergency. In this tutorial, GreatScott! will walk you through how to build an emergency hand-cranked powerbank generator to charge your phone in a situation like that.

Image for post
Image for post

In the YouTube video below, GreatScott! spends a lot of time thoroughly explaining how this hand-cranked generator works, and why his initial designs failed. Originally he was planning on using a BLDC (brushless direct current) motor like you’d use for a drone. But those are designed to run at a high RPM, which means they have to be turned at a high RPM to produce a sufficient amount of power to charge a powerbank. He was able to improve the low RPM performance a bit by rewinding the motor, but ultimately it just wasn’t enough.

Switching to a geared DC motor dramatically improved the performance. Geared motors take the high RPM output of a DC motor and gear it down, reducing the speed and increasing the torque. The opposite is also true: turning the output shaft at a hand-crank speed spins the motor itself quickly and generates enough power to charge the powerbank’s battery. With that in mind, it’s a simple matter of connecting the motor leads to the battery. A 3D-printed case holds everything together, and a printed hand crank is used to turn the shaft. It would take several hours to fully charge your phone with this, but a few minutes should be enough to place a call in an emergency.

Image for post
Image for post

Hackster Blog

Hackster.io,

Cameron Coward

Written by

Author, writer, maker, and a former mechanical designer. www.cameroncoward.com @cameron_coward

Hackster Blog

Hackster.io, an Avnet community, is the world’s largest network for hardware & software developers. With 1 million members and 17,000+ projects, beginners and professionals can learn and share how to build robotics, industrial automation systems, AI-powered machines, and more.

Cameron Coward

Written by

Author, writer, maker, and a former mechanical designer. www.cameroncoward.com @cameron_coward

Hackster Blog

Hackster.io, an Avnet community, is the world’s largest network for hardware & software developers. With 1 million members and 17,000+ projects, beginners and professionals can learn and share how to build robotics, industrial automation systems, AI-powered machines, and more.

Medium is an open platform where 170 million readers come to find insightful and dynamic thinking. Here, expert and undiscovered voices alike dive into the heart of any topic and bring new ideas to the surface. Learn more

Follow the writers, publications, and topics that matter to you, and you’ll see them on your homepage and in your inbox. Explore

If you have a story to tell, knowledge to share, or a perspective to offer — welcome home. It’s easy and free to post your thinking on any topic. Write on Medium

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store