chucky

Does anyone know if the Dymotec S12 limits it's output current/power (sometimes referred to as regulated)?

tatfiend 

Per the B&M web site yes it is. it states "Electronically regulated voltage". So was the discontinued S6.

https://www.bumm.de/docu/112e.htm

With some of the current higher power LED lights regulated dynamos are actually a disadvantage as they need the higher power of an unregulated dynamo to reach full output. Also no 12v LED dynamo bike headlights are currently made that I know of. Per my understanding the regulation is typically just a pair of zener diodes in the dynamo that clip the output at a predetermined level though the Dymotec regulation may be more sophisticated considering the price of the S12.

To me the currently available LED 6v dynamo lights have made the S12 obsolete except possibly for special purposes.

chucky

Hmmm, it goes on to specify that "the maximum permissible voltage is defined via electronic control", but it doesn't say that the power or current is limited. I remember there being some german site which tested the electrical characteristics of all the dynamos available. Maybe I should check that.

Yup. That's why I was asking.

I think I could do much better rolling my own, including my own regulation circuit.

tatfiend 

Typically in bicycle dynamos the current is limited by internal impedance. A bike dynamo typically seems to top out in the .6 Amp range maximum regardless of the voltage reached. Above minimum speed pretty much a constant current source.

At higher speeds the voltage on an unregulated unit can get quite high but the current is self limiting per graphs I have seen. Some lights such as the Supernova E3 Triple use this to draw more total power. Per an email I received from Supernova the Triple does not reach full light output until about 25 MPH when run off of a hub dynamo. I suspect that it would never reach full output if run off of a bottle dynamo such as the Dymotec 6.

Again per the graphs I have seen a 3 watt rated bottle dynamo can reach about 6 to 7 watts maximum actual power out while a hub dynamo can get closer to 12 to 14 watts out. Of course the input to achieve this hs to come from the rider.

chucky

I noticed that B&M is now selling a very nice AC->DC converter for cycling called the E-WERK. As the E-WERK is only supposed to be compatible with unregulated dynamos I contacted B&M about the regulation of the S12 and their response was:
I have to say that I'm very tempted to drop the 500 big ones for the S12 along with the E-WERK. Looks to be quite a useful combination for powering just about anything which can be reasonably powered by humans and more importantly has the quality construction necessary to survive the road vibration and general outdoor abuse of cycling in general.

tatfiend 

Manufacturers tech support frequently has the answers if they are any good.

Remember that a bottle dynamo is driven by a roller rotating against the tire sidewall and the more power you pull from it the more resistance to rotation there is. Bottle dynamos are best used with tires that have a dynamo drive track moulded into the sidewall such as Schwalbe city and touring tires do to prevent sidewall wear. Also the bottle dynamo can slip in wet weather if that is a concern to you. I recently bought the Dymotec 6 and installed it but have used it minimally so far. I have it feeding the Light On! Dymolight headlight and taillight and have Schwalbe Marathon Plus tires on the bike.

I had to make my own mounting bracket as nothing in the way of commercial dynamo brackets would fit my Swobo Dixon aluminum frame or fork. I am a hobbyist machinist so it was a interesting project. The bracket I made mounts the dynamo ahead of the fork on the right hand side.