Dynamo lights - Swapping an old halogen headlamp for a new LED one

[Big_Jimbo]

Can anyone more knowledgeable than I advise if I can simple swap my existing halogen headlamp out and replace with new fangled LED one?
Does it matter whether I have a tail lamp wired up as well? Can I mix an LED headlamp with an incandescent tail lamp? I know how to swap to lower wattage halogen headlamp bulbs depending whether I'm running a tail lamp, but I'm worried about frying something expensive if I just swap in a new LED head unit.

Thanks in advance
Jim

[IanW]

The answer is that you very probably can but it depends on ...

1) Is your "dynamo" (which is actually an alternator) a fairly conventional rim or hub dynamo?
I.e. one that is nominally capable of delivering 6 volts at up to 1/2 amp = 3 watts?

2) Does your existing wiring using a single core and thus uses the frame as the return electrical path?
Or does it use *2* wires/cores between the front light and the rear light?
Or is the rear light wired directly into the dynamo?

The ideal would be 2-core wires from the dynamo to the front light and then 2-core wires from the front light to the rear light.

But if your wiring is single-core then you will need to find which connections on each of the lights and the dynamo is grounded / earthed to the frame of the bicycle
and this is so that you know to connect the *other* connector to the wire.
Most lights will have an earth / ground symbol on the light itself or on the instructions.

A typical modern LED front light will have a pair of connectors for 2 wires incoming
and another separate pair of connectors for the rear light.
This is so that the front light can rectify the alternating current to 6-volts DC and stabilize it for use in both the front and rear lights.
Sometimes even providing a switched supply to the rear light so that the single switch on the front light operates both lights.

One significant advantage of many modern LED front and rear lights is that they have a so-called "stand-light"
which keeps the LEDs lit (perhaps at a lower brightness) for a few minutes even when bicycle and thus the dynamo is stopped.

So if you are going to the bother of switching over to an LED front light, then it would make a lot of sense to switch the rear to be LED also.
Is your existing rear light mounted to a rear carrier rack? Or to a mudguard? Or to a seat-stay? Or to a seat-post?
Do you have a particular attachment to the existing rear light? Even then you can get some LED replacement screw-in bulbs.

[mickeg]

I have many hours of use on a B&M LED Lumotec Oval (discontinued model) that is not hooked up to a tail light, no failure yet.  Maybe the trick is that you have to go as slow as me to avoid burning out any lights.

The comments by IanW are quite good, I do not have much to add.  As long as you keep your taillight wired parallel and not in series with your front light, your incandescent tail light should work fine with an LED head light. 

If you know which light you might want to buy, you could look for installation instructions from the manufacturer web site to see if there is any good information there on wiring and on use with or without a tail light.  My Lumotec has a couple little 2.8mm spade connectors specifically for tail light connection according to the instructions.

[Far-Oeuf]

I've just fitted a Supernova E3 Pro 2 headlight, no tail light.   It has a tail light wires coming from the headlight, and requires a DC powered tail light.   The manual says the tail light takes 0.4W (of 3W) when connected.

EDIT: the E3 Pro stand light is about 5 minutes.  The headlight stand-light also powers a rear light, if connected, but that reduces the over all lighted time slightly.

cheers,

[martinf]

Most, if not all, recent LED headlamps should work with or without a rear lamp.

Unless you have a specific reason for keeping a bulb-type rear lamp I would also advise replacing this with a good LED rear lamp. If you have a hub dynamo, wire the rear lamp to the connector(s) on the front lamp, so it is switched on or off with this. I have also run a set of LED lamps with the front and rear wired in parallel on a bottle dynamo, I had no problems with this setup.

My current favorites for rear lamps are the B&M Line Plus for rack mount and the B&M Secula for mudguard mount. The latter is not very expensive, and both have the advantage (important for me) of having a standlight feature, so they remain lit for a few minutes when stopped at a road junction or similar.

[Big_Jimbo]

Thanks for the advice fella's.
I used to run a rear mudguard lamp on a two wire system till it got knocked off in the bike shed at work (Grrr) The B&M Sucula looks best for a rear mudguard mounted light. The only reason I asked about keeping a bulb type rear light is I've got an old one on the shelf at home.

Maybe I'll have to see if Santa can stretch to an LED one for me...

[Danneaux]

Maybe I'll have to see if Santa can stretch to an LED one for me...

Don't forget to check eBay, Jim.

I just snagged a NOS B&M Toplight Line Plus LED taillight together with an extra single-hole mounting bracket for USD$9.99 postpaid. I ehm, "don't know about it" because it will be a gift from Santa (family) to me. Yes, I can act surprised! 

They do come available occasionally, so it pays to check in the run-up to Christmas as people anticipate upgrading and want to get rid of older models.

Best,

Dan.

[Big_Jimbo]

Well I can confirm that I simply swapped out the old halogen light for the new B&M Cyo Plus LED one and it works fine. It is substantially brighter than I expected and perhaps even brighter than I'd hoped for. I've no idea on the exact conversion between lux and lumens in "real world terms", the packaging claims 80 lux (rather than several thousand lumens of the cheap imported battery lights on a well known online auction site) but it's plenty bright enough for me.

Someone in my local bike shop said the B&M lights have a chip inside which automatically allows for a tail light or not, as required.
Anyway, thanks for the help and advice.
Jim

[Danneaux]

Thank *you*, Jim, for the thoughtful followup; so glad it worked well for you.

Your experience will help others with similar questions, I'm sure; nice to share the happy outcome.

All the best,

Dan.

[Big_Jimbo]

Well I took the plunge and got a B&M Secula rear mudguard (fender) light.
All I've got to do now is work out how to wire it up. There are two terminals at the bottom of the light that the pre-connected terminals would fit perfectly, but the wires stick out so horribly.
Does the collected wisdom of the forum know if the light unit comes apart to make the connection internally? The packaging doesn't make any mention of this and there are no instructions included.

[geocycle]

Well I took the plunge and got a B&M Secula rear mudguard (fender) light.
All I've got to do now is work out how to wire it up. There are two terminals at the bottom of the light that the pre-connected terminals would fit perfectly, but the wires stick out so horribly.
Does the collected wisdom of the forum know if the light unit comes apart to make the connection internally? The packaging doesn't make any mention of this and there are no instructions included.

No, but I'm interested in the answer as I also thought the spade connectors hung too low. That said, I've used the set up for a few years now and they haven't fallen off.

[Big_Jimbo]

Right I've fitted it.
A bit of concerted googling around seemed to show that the male spade connectors on the bottom of the tail light should be connected to the bare wires using the small top hat shaped plastic grommits included in the packet. You feed approx 5mm of each bare wire (twisted to hold it together) through the hole on the end (where your head would go if it were a top hat) and out of the top. You then bend it over into the even smaller notch in the side of the hat and scrunch the whole lot onto the spade connector. It seems to self crimp as it goes on and other forums (I know its disloyal to even look) seem to suggest it stays put like this for years.
This method seems to give a much nicer flush appearance than using the spade connectors they include in the packaging. Also I had no way of telling polarity so either I got it right first time, or some clever circuitry sorts it out for you.

A quick spin around the block confirms that it is really bright. I mean REALLY bright. I don't think it has too much of a beam like some LED rear lights have. This removes the unpleasantness if you're following in a group, but from my perspective (as the rider) it seems to have a really bright halo around a central reflector. I'll have to wait till the weekend to see what my riding buddies think for a more independent review, but so far, so excellent.