ok let me be clear… I dont want a “cant be done,not worth it” cop out answer, Im not asking about practicality. Im talking about possibilities.. I have taken aircraft electrical training but that was a couple years ago and had a pretty decent electrical understanding, let it slip and rusty…. answers preferred from people with electrical experience, and please dont bother me with suggestions of solar.. that said here’s the nitty gritty question…. I am aware of the nifty little hand crank dynamo cellphoneIpod chargers.. well I would like to possible makefindhack one to be able to charge something a little more sizable.. like a laptop or a 12 volt battery, I know that that is a pretty sizable challenge.. but Im not talking about a 15 minute charge time.. Im talking about hours of charging.. I get that, just curious if the dynamo has enough current output to be stepped up, and used as a trickle charger? if not please list a specific reason otherwise I will probably ignore your answer, people tend to try to answer things they dont understand, quite annoying,. the idea is like SHTF charger.. yes I am aware of solar power.. solar power doesnt work well indoors.. and it can be damaged. I like the flashlight size of the dynamos, quite portable. assuming its possible would it have to be stepped up? the whole stepping up and down, and coils part or my electrical understanding is so withered and rusted… basically. can I rig up a simple 2 contact setup to a 12 volt.. and crank like hell… or would it not have enough to begin the charging process. bonus points if you can break it down mathematically in amp hours.
One Comment
Rebecca H
on 25th Aug, 10 11:08pm
The problem is that most laptops use lithium ion cells in there battery packs. Lithium ion is designed to charge at a certain rate. You CAN make a hand crank charger, but to be powerful enough to charge a laptop at all would be something along the lines of wrist mountable. Using a gearing system, maybe even 1 designed to be like a 2 speed transmission, you could feasibly charge a laptop fully.
You will need to make the stator out of plastic as a ferromagnetic stator core will cause added resistance making it harder to turn. Then you will need a peak control circuit that will only allow current through when it reaches the set voltage to eliminate the resistance of getting it up to the needed voltage. In AC generators you just want the peak, anything less is wasted effort. The most efficient way to do this is to wind the stator for higher AC voltage than needed and step it down with a small transformer, then put the resulting AC through a bridge rectifier that feeds a capacitor rated for 40-50% more than needed to stabilize the pulsing DC current to a smooth DC flow.
A system like this will be a lot bigger than a simple dynamo flashlight so it will need to be mounted in some way. Wrist mounted kind of like a gauntlet would be a usable hand crank generator.
Thanks for the idea! I could make these just for the purpose you stated. As for the details of winding number, and what AWG, I would need further information on exactly what voltage and current to expect at output. Different batteries have different charge methods so specifics are needed.