How do you wire up a bottle dynamo?

I have a SON hub on my Quickbeam, driving an E6. I’ll get LED lights, but I have like 4 dynamo halogen lights, and 6 or 7 spare bulbs. My short term goal is to get more than one of them into use on more than one bike. I just built a very affordable Alfine dynamo hub, but realized the 19mm rim might not be the best match for the 53mm Big Apples on the gravel roadster. Probably wise, since today the rear SpeedDisc rim decided it was too small to keep the Big Apple seated. I don’t know if the bead broke, or what, but that tire will not go back on that rim… Anyway, I put the new wheel on the Ross, with an E6 I got from a friend. Works great, but I’ll probably have to trim the lens tabs to work right.

So… the new plan is to set up the gravel roadster with a bottle dynamo I got from another friend.

Except I have no idea how to work those things. Surprisingly little internet resources are devoted to the question of how to wire a bottle dynamo to an E6, and half of those use clever black bottle dynamos with two explicit wire mounts. This one has a little capped-off recess that probably takes one wire. I found a picture that looked like the ‘extra’ lead is grounded to the mounting bolt, so I decided to run with it.

I put a wheel with an inflated tire into a truing stand in order to test my dynamo, and started cutting off perfectly good spade connectors and stripping wires to get some bare leads. I connected the wires to various parts of the dynamo, and held the wheel against the tire. What seems to work is obvious in hindsight. One lead goes through the little plastic cap – through a hole, doubled back through another hole, and screwed into the bottom of the bottle, and the other lead goes to the connection bracket. Hold it all together and put the dynamo head against a spinning tire, and the light shines! Pretty magical.

I bought some shrink-tube and a little box of circular wire-ends, but didn’t install them. I went for a bike-ride instead. Two, actually.



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UI/UX Designer, bike nerd, artist.

6 thoughts on “How do you wire up a bottle dynamo?”

  1. One idea , use lamp cord ,2 wire 18 guage. take your wire ends crimp on .Wire is usually coded with a ridge. select one for ground ,bolt it on grd . Tie wrap wires to frame. The one advantage of his ,is current does not go thru headset.A 2 wire 6 volt d.c. circuit . And sing , this little light of mine ! You have substituted a wire for the frame.

  2. Ah, lamp cord. My lights all have wires. I would’ve used the Lumotec, which already has an iffy connection to the spades, but I was afraid the switch in the back would be bumped by my front bag too easily.
    If I ever get the soldering chops to build an LED light, I’ll remember the 18 gauge lamp cord. I think people use 16 gauge for speaker wire.

  3. This text really made me smarter! I was always wandering how just one wire goes to the light and still it works. Thanks Philip!

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