Bike dynamo charger

[joff]

Hello All,
I hope you can help me with a project that I have. I am a long distance cycle tourist and need to charge AA batterys for cameras etc while on the road. Solar chargers are ok but a bit bulky, so my question is can I use the bikes bottle dynamo to charge the batterys? If so do you have a diagram I could see?
Many thanks in advance,
Joff

 

[bogdanfirst]

there are a few things you need to consider..how many batteries, and what current to charge them with?
what voltage is the dinamo.....?
you must also think that the voltage you obtain at the output of it varies, for example for a 12V one you can actually get short spikes of 30V
i think of an idea like to use a diode, a capacitor of a large value, and a stabilizer, like a 5V one....and charge 2 batts in serie.
i dont know there are many possibilities, ill see what the others say.

 

[McGuinn]

Joff, From my experience with dynamos, I found that they can wear out their path on the tyre wall and cause tube bubbles and locked front/rear wheels. To be avoided...! Also, they cause some additional drag on the bike and over a long run this will be noticable. My advice... handle-bar mounted solar panels or a windmill! ;-)

 

[kinjalgp]

Instead of driving the dynamo with tyre, how about coupling it to the chain? It will work out better than with the traditional tyre scheme.

 

[bogdanfirst]

well, sine you are talking about how to get the energy how about this: buy a "bucket" of small solar cells and attach them on the bike all ober the place.

 

[kinjalgp]

Bogdanfirst, what if the bike falls? Your "bucket" will turn into pieces of glass.

 

[john1]

Hi joff,

I agree with McGuinn,
they're ok for occasional use but anything on a regular
basis and the tyre suffers.
Have you considered a hub dynamo?
They dont damage anything and the 'drag' is a lot less
than the bottle type.

In answer to your question, yes you could charge small
batteries using the bicycles dynamo.
The small bottle type dynamoes are strictly speaking
not dynamos at all, they are alternators.
They wont deliver much current, i think the windings
may be quite thin wire.
You would need to rectify, probably a diode bridge,
and also put some sort of voltage limiter across the
battery, maybe a zener diode. dont worry about a series
resistor, its own internal resistance limits its max
current to about half an amp (or less).

Regards, John

 

[bogdanfirst]

ill also put a resistor in series with the bridge and a capacitor after the bridge.
and yes, i only said it as a posibility with the "bucket" of cells because i saw a guy on tv that did that.