Dyno light wiring - Kim?

[ElyDave]

Set up on the DF roadbike was

Hub - twisted pair --> front light and USB Werk
Front light output --> rear light

Now transferring this to the Cruzbike where the front wheel is at the back.  Any foreseeable problems if I do
Dyno hub - twisted pair --> rear light and USB Werk
Twisted pair at rear light and run cable back to front light input.

Would be one less cable running the length of the frame

[Brucey]

when you turn the front light off (or a wiring fault turns it off accidentally), the rear light (wired in parallel) will see the full output of the generator. This may well cause it to expire; the manufacturers usually explicitly prohibit this arrangement.

cheers

[ElyDave]

good points, that's why I'm not an eletrician

[SA_SA_SA_SA]

when you turn the front light off (or a wiring fault turns it off accidentally), the rear light (wired in parallel) will see the full output of the generator. This may well cause it to expire; the manufacturers usually explicitly prohibit this arrangement

Which annoys me as it is could easily happen accidentally or a person may want to limp home with dynamo rear lamp and spare battery front: surely the Stzvo should force manufacturers  to spend a few pennies more so that an independant  rear lamp can withstand the absence of front indefinitely...

[grams]

Every LED rear light I've seen advertises "overvoltage protection" which I've taken to mean they support this configuration (or at least, won't be killed by it).

(and my experience is they do work fine, except the Secula, which dies in seconds)

[Brucey]

Every LED rear light I've seen advertises "overvoltage protection" which I've taken to mean they support this configuration (or at least, won't be killed by it).

(and my experience is they do work fine, except the Secula, which dies in seconds)

other B&M models claim 'temporary protection' only eg

http://www.sjscycles.com/Instructions/Busch_&_Muller/Busch_&_Muller_Seculite_Light_Instructions.pdf

Basically they are telling you that the lamp will probably fail if you habitually ride around with it as the only load on a hub generator.

BTW if you want external voltage protection I think the shimano unit (that used to come with every hub generator) contains a thyristor style crowbar circuit. Even this can and does fail if too much is asked of it, too often.

cheers

[Kim]

I don't think I've got much to add, other than that you can simplify the wiring by riding backwards

[grams]

other B&M models claim 'temporary protection' only eg

While rummaging through a box of random stuff (looking for something unrelated) I found the backing card for my B&M Toplight Line Plus which says "if the headlight breaks down, the integrated overvoltage protection permanently protects the rear light." So both types exist.

[Brucey]

in which case it is presumably a matter of reading the small print very carefully and proceeding accordingly.

cheers

[mzjo]

If anyone needs one I have the Shimano protection device sitting in the garage and it could easily go in a jiffybag. I am never going to use it.

[ElyDave]

I still have the destructions for mine, so will check