Il problema dell'alimentazione elettrica per chi usa la bicicletta, sia nell'uso quotidiano che per viaggi di più giorni, sta diventando sempre più impegnativo. Serve sempre più energia elettrica non solo per illuminare la strada nelle buie ore della notte ma anche per alimentare il sempre crescente numero di dispositivi elettronici a cui non sappiamo più rinunciare. Questo sito vuole essere un primo passo per provare ad orientarsi nella non sempre facile scelta degli strumenti necessari per gestire in modo possibilmente autonomo le proprie necessità.

The electric power supply problem for people who like to cycle either in everyday use and along trips of several days, it's becoming increasingly challenging. More and more electricity is indeed required not only to illuminate the road in the dark hours of the night but also to feed the ever growing number of electronic devices that we can't live without. This site aims to be just a first step in the attempt to orientate the user in the not always easy commitment to choose the most appropriate tools.

Wednesday, 1 January 2014



There's a lot of talking about actual available power using an hub dynamo !!

OK, here below some considerations and conclusions:

1. Hub dynamos are universally rated nominal 3W-6V: nonetheless voltage can reach as up to 50V at no-load and power can slightly be more than 3W at speeds over 20 km/h.

2. If dynamo output is directly connected over an ohmic load then transferred power is stricktly bound to be equal to U^2/R but if instead of a resistor you use a rectifier with a built-in or an external buffer battery then transferred power can well exceed 3W, in both cases indeed the battery will be able to temporarily receive more power than a static ohmic resistor. So if you have the e-werk output set for instance at 5.6V with connected a 10 ohm resistor you won’t have more than 3.14W (provided that you pedal fast enough!) but if instead of 10 ohm you use a 5 ohm resistor you will never have the calculated 6.27 W ... believe me !!!

Here below however some considerations:

1. From SON technical documentation I’m reading that both SON28 and SONDelux are rated 6V/3W.

2. I’m also reading that, on a 28" wheel, nominal output is reached at about 16 km/h with a SON28 and at 19 km/h with a SONDelux.
3. Both dynamos feature an efficiency of 65% (approx) at 15km/h with a 700c-28” wheel
4. Now looking at the power plot available in the SON technical documentation in correspondence of 16 and 19 km/h respectively for SON28 and SONDelux I’m reading an input mechanical power of 4.3W … that multiplied for the declared 65% efficiency factor it makes an equivalent transferred power of 2.8W, something less the claimed rated power, this fact not surprising too much however since load conditions are a very general "lights switched-on" !!!
5. Of course going faster available power shall increase accordingly
6. With a SON28 at 20 km/h we will have an input mechanical power of 5.2W … that, again, multiplied for the declared 65% efficiency factor it will make something like 3.38W … better than nothing !!!
7. Now it comes the e-werk, whose efficiency we might assume to be something around 70%
8. So the 3.38W available at the output of the generator at 20 km/h shall have to be reduced to a miserable 2.37W (3.38X0.7=2.37) … not too much indeed 
9. CONCLUSION: dynamo + e-werk = overall efficiency < 50% !!!!

BRUSHLESS DYNAMO PROTYPE (in fase di studio)

- Dinamo al mozzo
- Convertitore ac/dc
- Batteria tampone
- Porta multipla USB