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.
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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