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I am making a project to charge a cell phone battery using a dynamo,but i don't know how to start about.also let me know about the power ratings of the dynamo to be used for charging a 3.7V,1000mA cellphone battery using a rechargable battery.

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There are a lot of dynamo chargers out there, and they work so and so because you need to feed a very precise and limited current to the battery. A (maybe) better solution would be with a buffering capacitor and a "constant" current output, or at least something that limits the current output, as that's what may damage your battery. – clabacchio♦ Mar 15 '12 at 18:49
For precisely rated dynamo you will need an accurate human, rotating crank handle at exact speed. Dynamos can be rated precisely for many values, but not for their top mechanical speed. So to limit speed, make the crank handle as long as possible, so the velocity will be limited by anatomy. Say 2 feet handle or longer will guarantee limited velocity. – Rocket Surgeon Jun 14 '12 at 2:56

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If excessive quality is not an aim :-) then you are not liable to do too much harm most of the time if Vmax_alternator measured at the battery terminals is clamped to <= 4V and if current is limited to <= the 1 hour battery rate. eg 1000 mA for a 1000 mAh LiIon battery.

THe above means that while the battery terminal potential MUST NOT be allowed to be raised to more than 4.0V by the alternator, if the voltage is limited by clamping then it MUST be the alternator and not the battery that is clamped. Clamping the battery to 4V may cause battery and clamp to emit magic smoke.

This circuit also may cause the battery to emit magic smoke under unusual but possible conditions - eg if deeply discharged

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