byrd48

Hi,
I just ordered a dynamo hub but I have not purchased the lights yet. I was looking at the AXA Luxx 70 plus for the front and a B&M Toplight Mini or B&M Toplight Plus. Are these wired in parallel or in a series? I presume that if the taillight has the standlight feature, then it can be parallel, but if it does not, then it would need to be in a series from the headlight? I'm also assuming that since they are both LED models, that there should be no compatibility issues?
Thanks for any input.
Jon

FBinNY 

There may be exceptions, but just about all bike lights are wired in parallel for two reasons.

The first, is that series circuits split voltage, so lights wired this way would always have to be wired as sets, with no change in the load of either.

The second, and maybe more important for bicyclists, is that in a series circuit, the failure of either light would kill both. (remember Christmas tree lightsets (fun and games years ago)? Anyway, you wouldn't want to be totally without lights if either failed.

byrd48

Thanks!
I just ordered the lights from Amazon.de in Germany. The order form said 5 - 10 working days, but when I got the email confirmation, it said 4 - 6 weeks. Ouch. I guess you have to wait a while to save some money... It was about $50 less than I could find domestic...

Chesterton

FBinNY, do you mean that the internal wiring is parallel? My Busch & Muller setup runs has wires that run from the hub to the headlight and back, and then wires from the headlight to the taillight and back to a grounding loop on the headlight's mounting bracket. The switch on the headlight also turns off the taillight. I'm pretty sure if the taillight failed the headlight would continue to work, but if the headlight failed, both would turn off.

Series or parallel aside, Jon's biggest issue will probably be connecting them. The taillight probably takes a bare wire connection, so that part is easy, but the headlight may use crimped spade connectors. If the light doesn't come with a precrimped wire you will have to procure and affix them yourself.

Zip ties are handy for securing the wire to the frame between the headlight and taillight.

FBinNY 

The switch may be in the headlight, but the circuit should be (almost has to be) parallel. Otherwise the headlight wouldn't work when there was no taillight attached. (simple enough test)

I suspect it's wired that way because the internal backup battery that keeps lights on when you stop, and the charging circuit that supports it are both part of the headlight module. Otherwise, they'd have to have them in the taillight also.

Another way to know if a circuit is seris or parallel, is to compare the voltages of the source and bulbs. Series circuits step the voltage down at each load, so a 12v generator would use 2 6v volt bulbs, while a parallel circuit, would use 2 12v bulbs.

dscheidt

No batteries, it's all done with capacitors. And tail lights, fitted with standlights (don't buy anything else!) have their own cap, and thus work even if you unplug them, while the standilght is on. Supernova used to power their taillight standlight from the headlight. I don't know if they still do. I think that's stupid, for lots of reasons, but mostly because it reduces reliability with no other benefit.

fietsbob

+1, the taillight power comes off the headlight, headlight comes off the Alternator -hub dynamo.

think the loads are similar to back in the bulb days , .6w for the taillight the rest of the 3w for the headlight ..

So, some Hubs , only put out 2.4w, there the taillight has to run off it's own battery .

my B&M 4D senso Plus , uses the AA for the standlight, lack of motion turns it off .. in a couple minutes
in what was the off switch position on the 4D senso is the power from the hub, but no standlight.

when I used it with the E6 halogen headlight (2.4w bulb) which also had no standlight stopping ,
the lights went out.
unless the battery was used in the taillight too .

wanted to use a dyno hub on my Brompton .. the Lyt BN which was to be the new OEM pick, lacks a standlight.

I returned it.. got the Eyc instead.


the E6 2 headlight setup was series .. secondary light switch was wired, on and bypass-through ,
primary is on & off..