USB addon for ST1


I found this DIY site for adding a USB port to your ST1 tied into the electrical system. It is from a German site so the translation was done by Google Translate so bear that in mind. I would really like to try this and being as you are piggy backing off the existing connector that the front headlight uses it can be added and removed without altering the bike. I have been looking for the connector but have been unsuccessful so far.

Summer is coming - now is gone. Wide and long. With Navi and GPS tracking. Only the iPhone battery does not want to join -. Around 3 hours, the Natel switched from
the first attempt has to load the cell phone while driving occurred with Zzing module (Smartphone version) (and yes, my Stromer has a hub dynamo). Unfortunately, the part has never worked properly -. Had no luck charging with the Dynamo Power the phone
Well, we do it it myself - DC / DC converter - Stromer battery to 5V / 500mA.

Dar the DC / DC voltage converter with input voltages of Recom between 9 and 72V works, it can be used in other e-bikes (flyers installation instructions coming soon) without special.

!!! Important: I am not responsible for damage caused by the construction of the charger. The circuit is not intended for individuals who have previously had nothing to do with the electronics. Manipulation of the Stromer wiring can damage the electronics and void the warranty.

The DC / DC converter is so small that it can be hidden easily in the battery compartment of the Stromer.

"Ingredients" list:
  • voltage converter R-78HB5.0-0.5 (at 16.80 CHF)
  • 2 x 75k Ohm resistor (1%) - (Optional: only iPhone)
  • 2 x resistance 49.9k ohms (1%) - (Optional: only iPhone)
  • Stromer connector (Optional)
  • USB connector (Optional)
  • ON / OFF slide switch (eg Item No: 202374.)
All together it cost me about 25 CHF.


The circuit was reduced to the absolute minimum in the as DC / DC voltage converter of Recom R-78HB5.0-0.5 was used. The Recom operates with input voltages from 9 to 72 volts and the output produced beautiful stabilized 5V with max. 500mA - which is sufficient for iPhone navigation and tracking.

The resistors R1 / R3 and R2 / R4 are nothing more than a voltage divider. Needed only for the iPhone ung say the Natel how to draw maximum current from the charger much. Here the USB pins D and D + to exactly 2 volts are set = charger with max. 500mA. Who wants to use a different phone needs these resistors are not installed.

The Power ON / OFF switch is designed to disconnect your transducer from the battery. Whether it is necessary? Maybe then if the Stromer is not run for longer time. The converter in idle mode moves from the battery approximately 1.5mA.

As mentioned above, the transducer itself was installed in my Stromer in the battery compartment (see figure below).

The USB Charging Cable for iPhone I have hidden in the spiral together with rear brake cable and interface cable.

There are no dedicated board - because the circuit is so simple, universal board can be used. I myself have cut out the USB jack with a piece of board from a defective USB hub.

If, however, more "rebuilder" report, I can make design and produce a PCB.


Staff member
Hi @CptPalmer thanks for sharing this awesome DIY article! Out of respect for the original content creator I've removed the images, quoted the post and made sure to reference the link. I respect and appreciate the work this person has done but also that you've shared it and I think this is the most appropriate way to reference it :)