Is there wiring diagrams i can look at to get an idea on how to wire up this bottleneck dynamo to my bike and maby trailer. I've been through pages of internet blah but found nothing yet help please?

  • For lighting a trailer, see also bicycles.stackexchange.com/questions/35223/…
    – armb
    Commented Mar 6, 2017 at 17:27
  • "this bottleneck dynamo". which one, exactly?
    – Paul H
    Commented Mar 6, 2017 at 17:50
  • The main problem with a bottleneck dynamo will reside in the fact that they have low power output of around 3W at 6V meaning grossly 0.5A. Typically they are just meant to power a front bulb and low power rear bulb. There will be hardly anything left for a third bulb.
    – Carel
    Commented Mar 6, 2017 at 18:13
  • 1
    tried to rescue the question through edits but it's still too vague.
    – RoboKaren
    Commented Mar 6, 2017 at 18:15
  • 1
    Dynamos put out around 6 volts of Alternating Current. So it doesn't matter how you wire it as long as the frame connection is good at each light and at the fork, and that the single wire goes from dynamo to each light fitting. You might not get a good frame contact to the trailer so consider running two wires. A coiled wire will survive longer than a flat wire.
    – Criggie
    Commented Mar 7, 2017 at 1:34

2 Answers 2


It might help if you gave more details about your dynamo, and/or what your problem is.

There are basically three different dynamo wiring systems.

  • Single wire, uses the frame as a return ("earth"), relying on the bearings in your headset being conductive between frame and forks, and clamps or mounting bolts being electrically connected to the frame.
  • Twin wire, but one of them is electrically connected to the frame.
  • Twin wire, isolated.

Similarly lights designed for use with a dynamo. So the main thing is just to be sure that if the lights and dynamo have frame connections, they are consistent. If there is a pair of wires, typically one of them has a stripe on and is the earth wire.

For a trailer, the main thing is going to be reliable connectors that you can easily connect and disconnect. If it lives up to its advertising (and I don't know if it will), this system might help (and it also has some wiring diagrams that might be useful to you anyway: Dyna-Snap). Otherwise maybe something like Anderson Powerpole, or TC-2C1PT


@armb has a good response re: wiring.

Supplementing that, I wouldn't try to wire your trailer with it. You have a little bottle dynamo (also known as friction dynamo) on your front tire. They only put out 5-6 watts on a good day with dry tires (see footnote). Trying to get out more will really stress out the dynamo. They have short lifespans to begin with and you'll only make it shorter. Your front headlight will likely consume 5 watts by itself, leaving 1 watt for the taillight.

And as @armb notes, you'll have a problem with the electrical connection - especially if your dynamo is a single-wire design using frame ground.

If you really want dynamo lights for your trailer, you could either put a bottle dynamo on your trailer itself or put a dynamo hub on one of the trailer wheels.

tl;dr: just get a USB-rechargeable rear-light for your trailer.

Footnote: Some friction dynamos do advertise more power (some up to 24 watts) but I'm highly suspect of them. That's a lot of power to rub off the tire sidewalls and I think you'll find it comes at the expense of shortened tire life, shortened friction wheel life, shortened dynamo life, and considerable drag on the tire.

  • Standard dynamo output is 3W, 2.4W front light, 0.6W rear light. With modern red LED rear lights being so efficient, running two rear lights from a dynamo is plausible. The problem with using another dynamo on the trailer just for a rear light is that it might just burn out the light, but even if it's regulated the regulator won't be designed to dump that much excess power.
    – armb
    Commented Mar 7, 2017 at 7:57
  • (On the other hand, I do agree with your conclusion. In fact I use a battery powered rear light even on a bike with a dynamo. (And when I was using a trailer bike, used a battery rear light on that too.))
    – armb
    Commented Mar 7, 2017 at 8:01
  • peterwhitecycles.com/wiringinstructions.php has a list of rear lights that will survive the full output of a dynamo, under "What NOT To Do!". (It's described as 'rear lights which will survive being still connected to a hub dynamo if you turn the front light off', but that's effectively the same.)
    – armb
    Commented Mar 7, 2017 at 21:27

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