Cyclus – A Personal Electricity Generator

Cyclus USB charger on desktSatoshi Yanagisawa is a sustainable designer based in Farnham in the south-east of England.  He’s developed “Cyclus“, a concept for a wind-up USB charger that will give around 30 minutes juice for a couple of twists.  Based on a spring and DC motor, this is simple technology in a great design and is a far more elegant solution than other solutions such solar (photovoltaic) chargers or external batteries.  In particular, the Cyclus can be easily carried with you, doesn’t need the sun, doesn’t weigh much and is infinitely re-chargeable. 

Cyclus in useCyclus Exploded View

It’s certainly not the first wind-up charger but it’s definitely the best looking – this is one design concept that I hope makes it to product.


  1. engineeringthoughts says

    This makes it seem trivial to generate power. Lets take the claims at face value.

    A phone charging off a USB port will pull 500mA max at 5V – that is 2.5 watts, completely reasonable for a battery that needs to be charged. 2.5 watts for the claimed 30 minutes is 1.25 watt hours. 1.25 watt hours is 4500 Joules.

    This is an ENORMOUS amount of energy to store in a small spring. Energy stored in a coil spring is .5*k*x*x – a very stiff spring would have a K value of 90lbs/in (takes 90 pounds force to compress/extend by 1 inch)***.

    You would have to compress or extend said spring about 29 inches to get this amount of potential energy…. 29in*90lb/in = 2610lb

    It’s fairly unreasonable to expect a human to apply over 2 short tons of push/pull – even 90 pounds is unreasonable.

    Now, I know it’s a twisting action – power springs are more abstract to the layman than the ubiquitous coil spring.

    Even if we used a power spring (the style used in clocks, seat belts, wind up toys, etc.) – it would need to be gigantic and would be equally difficult to “compress” VIA twisting.

    Designers – please stop trivializing power generation! It makes my job (and the jobs of others working in the space of small scale energy conversion) more difficult and fails to manage customer expectation. The internet has a huge amount of resources to do quick feasibility gut checks.

    *** I did the calculation using more traditional units using newtons, meters, etc. pounds (force) and inches are just for reader ease.