Sometimes we travel together with electronic companions. To keep them alive during the trip, we build the ‘Minimal-Charger’. It’s well described and explained on Unfortunately only in German. You can ask us for help.

The circuit is very simple and easy to understand. Basically, it consists of a bridge rectifier and a smoothing capacitor. The voltage is limited by a Zener diode to 5.1 V. Therefore the circuit is fairly ineffective (but often sufficient), but very easy to build. The entire system will cost only a few Euros.

We equipped the Charger Tamiya coupling for the Dynamo and a micro USB connection for the devices. To dissipate the heat of the Zener diode, we used piece of a can.

3 Responses to Minimal-Charger

  • robert niestroj

    Great Idea, this cycling charger!
    I can see you are using three capacitors instead of two (like in the original circuit diagram). Can you tell me why and which capacity you used?
    Kind regards

  • Happy Homeless Hippie
    Happy Homeless Hippie

    Hi Robert,
    sorry its been ages ago, I don’t remember.
    I remember that this charger didn’t work that well.

    I finally gave up and bought the bumm e-werk. This charges quite well, but somehow they die quite fast as well. Never heard that someone else saying this, but it’s my experience. Four times they gave up working, once the battery melted in my luggage. And now I’m sitting here in India, and still carrying two damaged ones with me. Not reliable and really expensive.
    Have to say, people at bumm are nice, they replaced my charger a few times (~2 times) without any trouble. Maybe I better travel without electricity then with something not reliable.

    The really best one is Forumslader!!!
    But its all in german
    You can order one set there and build it yourself, or get a ready made one.
    Think for efficiency its one of the best, and its made by cycle touring people.
    The people super friendly.
    …. unfortunately I destroyed that charger as well, but totally my fault ;)

    Cycling through central Asia we made great experience with solar chargers. Would recommend this as well. But not a good idea for cloudy rainy European winters.

  • Ome Ko

    There’s another beautiful cyclist who built the minimallader and used it as well (me). I’m quite happy with it; it has never let me down over the past few years. It’s serving as a backup in case the forumslader stops working.
    Currently the Forumslader is not available due to component shortages, so I’m charging my stuff with the good old Minimal-Lader.

    Probably it has 3 capacitors because the first one was not available in the right capacity. I had to use two connected in serie there.

    Details (in Dutch) are on

    I tried to post the googletranslate link but wordpress thinks it’s spam then.


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