Dynamo + USB + Front & Rear Lights setup

Gear / Kit

There are many pros and cons to discuss on whether a dynamo should be used or not. This is not the article for it, it assumes you’ve weighed those up and have gone the dynamo route.

Now, you have a dynamo installed (in my case SON Deluxe on the HUNT’s SuperDura Dynamo Wheelset). But you are not using it. The next decision is do you want to connect only lights or you also want a USB charger in there. I’ve decided to have all of those (again the reasons are personal).

Lights and USB charger

So here’s what my choices for lights and USB charger look like:

Good alternatives for the front light would be the

And alternatives for USB chargers:

Additional connectors

Connecting them together

There are multiple ways to connect all components together. This is where I struggled the most in deciding. But a few key considerations made the decisions for me.

  • Easily switch off the lights and use them during the night and be able to charge using the USB during the day. Have the option to charge and have the lights on if needed.
  • The USB charger didn’t need to disconnect from the system as it would only draw energy if something is plugged in the charger (if you prefer to be able to switch it off, you can use the kLite switch harness).
  • I wanted to be able to disconnect all elements at any point for either swapping them out or maintenance. This meant no permanent soldering, they would all connect via connectors.

A note – my Supernova front light has a on/off switch which is very handy as I can turn it on and off while riding. Because of that, I didn’t need to have a separate switch. If your light doesn’t have a switch, you might need to either a) be able to disconnect the cable or b) install the above kLite switch.

The USB charger really doesn’t need to disconnect (in my opinion) and this could simplify your system. But if you wanted to, then you can consider unplugging the cable (possible with my system below) or adding another switch (really?).

The system

The barebones of the system:

Click to enlarge

The system with some comments:

Click to enlarge

Real components preview:

Click to enlarge

This system is what I would have liked to see when making my decisions. It does look quite daunting if you haven’t been exposed to something like this before. I will add some more details based on comments and requests.

An important note is that I didn’t trust myself to do the soldering and asked Mike from Tony Butterworth Cycles (Sheffield) to do it for me. He did an amazing job, but while watching him do it, I was glad I didn’t do it myself. In particular, soldering the wires into the connectors is quite delicate and I think you need to know what you are doing.

You can skip the connectors and the junction box and just solder everything together, that would be the simplest solution. It is perfectly fine and would function no worse at all. In fact, it might be more weather-proof depending on your skills.

However, I do love the connectors and the adaptability of this system. It means I can swap any component (apart from the junction box which is soldered to the front light) if I wanted to fairly easily without disrupting the rest of the components.

Also, the SON adapter that connects to the dynamo is very solid and has an extremely good connection (it won’t budge). Which is important and I prefer it to the other alternatives I’ve seen out there.

Finally, make sure to follow the instructions in the junction box kit. It comes with heat shrink wraps which you need to put around all the soldered bits (connector, junction box). Make sure you put the heat shrinks onto the cable before you solder components together, otherwise you won’t be able to put them on afterwards.

Minimum components cost

Supernova E3 Pro 2 Dynamo Front Light£119.99
Supernova E3 Dynamo Tail Light 2 – Seat Post Fitting54.99
kLite USB charger144
SON Coaxial Junction Box –
Male Connector w/ Coaxial Adapter – 80 cm
SON 2-Pole Connection for SON-Coaxial Cable –
Male Connector

You will have to include cost for postage, re-building your existing front wheel with the dynamo hub, and potentially welding work by someone experienced. However, this is an incredibly robust and versatile setup at the above price as of date 20th June 2020.


I love this system and it is the result of months reading and researching (you don’t want to see my notes). Many of the components can be argued, but this is not the idea of this post (it’ll be too long). It simply shows you my solution. If you have any comments and questions please put them bellow and I will update the article respectively.

2 thoughts on “Dynamo + USB + Front & Rear Lights setup

  1. Hi, really good easy-to-understand piece.

    For something that seems like such an obvious requirement for the modern bike tourer / bike packer etc, the industry seems to be so disinterested in providing user friendly hassle free solutions to Dynamo powered USB/Light setups.

    I have an Exposure Revo light which I want to setup in a similar way, but with a means to switch between. If I were to set up like you have in your very helpful diagram, if I were to simply unplug the input cable from the Revo, theoretically, would that send all Dynamo power towards the USB that would be directed via the junction? Likewise, if I were to simply unplug the USB from whatever device I was charging, would the same apply to the lights? I can accept that running both lights and USB simultaneously would result in a reduced performance for both, but I just want to reassure myself that when unplugging one, all the power source would find its way to the other.

    Ideally, I’d like the switch option, but I’m not too sure what the best option for this would be, and where in the wiring sequence it would end up.

    If you’ve any thoughts, I’d appreciate them.


    1. Hi David,

      I am grateful for your feedback and very glad that you find the article useful. It is precisely what I was looking for myself when setting things up – something easy to understand, but since there wasn’t one I felt I should write down what I’ve learned.

      To your questions:

      “if I were to simply unplug the input cable from the Revo, theoretically, would that send all Dynamo power towards the USB that would be directed via the junction”

      In my diagram, the light is soldered permanently to the junction box, so you will not be able to unplug it from there. BUT the supernova has an ON/OFF switch at the back, which essentially unplugs it, which is why I went down the path you see in the diagram.

      I just had a look at the Revo light. It seems to have 2 ports at the back. Input and output. My Supernova does not have those (it just has permanent cables coming out of it and an on/off switch). In your case, if you use the exact same setup as mine and permanently solder a wire into the SON Junction Box, then you can “unplug” your Revo light by simply unplugging the wire from behind the light. That would be your version of the on/off switch and it should act otherwise in the exact same way.

      Unplug light (this will also unplug the rear light)
      Revo light (remove cable from the back of the light) ---> SON Junction box

      Plug light into the system (this will also run the rear light)
      Revo light (plug cable in at the back) ---> SON Junction box

      For a “neater” solution, you can use something like the kLight switch button and solder it between your Revo light and the SON Junction Box, so you will end up with:

      Using a switch button to turn the light on/off
      Revo light ---> kLight switch (or similar) ---> SON Junction box

      But this is not necessary if you can unplug the cable from the light. It might just be easier to use (pressing a button vs fiddling with wires).

      “Likewise, if I were to simply unplug the USB from whatever device I was charging, would the same apply to the lights?”

      Yes, it would direct all the power to the light. However, I found no need of unplugging the USB charger itself, because it would not draw any energy (or just insignificant amount – haven’t tested this) when nothing was plugged into the USB charger.

      I would simply have 3 options:

      • Use only the light – switch the light on, not plug anything in the USB charger
      • Use only the USB charger – switch the light off, plug an external battery in the USB charger
      • Use both the light and the USB charger – switch the light on, plug an external battery in the USB charger (I don’t think I ever did this)

      It sounds like that setup might do all you need it to overall.

      Please let me know if the above comments make sense or if you would like me to do a diagram of what I’m trying to describe to visualise it better?

Leave a Reply

Your email address will not be published. Required fields are marked *