# Thread: Tiny wind turbine to charge a cellphone battery

1. Hi, I've been searching in the web for a while and I see now that I need help in this project.
The idea is to use a small wind turbine in a ventilation shaft and with this movement charge a sealed lean-acid battery to store the energy, later on I would connect a cellphone charger to the battery to charge it.
This would be an emergency system and it won't be necessary to fully charge the cellphone.

Reading through the web about wind turbines, to store the energy it says that I would need a charge controller to avoid making damage to the lean-acid battery.
Also it's in my understanding that the energy generated from this kind of energy through a generator comes as DC, and it turns out that cellphone batteries also use DC electric so my guess is that I don't need a power inverter to plug the cellphone to the lean-acid battery, I would just need another charge controller.

Finally, I declare myself as a person that has no idea about this kind of things and I really need easy explanations to understand this stuff.
Thanks anyway

2.

3. First of all, what is the point of this device? Why not charge the phone with a regular cell phone charger plugged into an electrical outlet?

4. Lack of access to an outlet. Might be good for hikers and the like. I know I ran into trouble while nowhere near an outlet after being out in the field over 10 hours and the damned battery died at the worst possible moment.
Managed to get myself out of the bind- but it wasn't easy...

5. In my university, it's pretty common to run out of battery at the end of the day. People rarely carries the chargers with them, so it would make things easier in emergency situations.

6. I'm trying to picture a situation where it would be easier to carry around a wind turbine than a charger or extra charged battery. But anyway, to answer the original question, your cell phone will need a d-c voltage equal to whatever voltage is stamped on the charger that came with your phone. Mine is 4.75 volts. The generator could be either a-c or d-c. If it's a-c its output would need to be rectified to d-c. The voltage output of the generator will vary depending on the speed of the turbine that is driving it, so you'd need a regulator to keep from overcharging the 4.75 volt battery.

7. Why not a solar powered battery recharger? Wouldn't it do as well? Smaller too.

Solar Chargers for iPhone, iPhone 4, iPhone 4s, iPhone 5, Droid, EVO HTC and more

8. Something tells me a wind turbine wouldn't work terribly well, considering most people are inside when they need to charge their phone. Asides from that, you'd need a windy area. Couple that with having to compete with already effective methods of charging, and there is virtually no market for the product.

9. Ok, so to answer my first question, I would need a dynamo of which size (does a generator/dynamo/RC motor work in the same way?) and to produce how many V to charge a lead-acid battery (Bateria 12v 7.2 Ah Sellada - \$ 12.500 en MercadoLibre) to store the energy here and to use it to charge smartphones?

10. Fingon,

A 12V car battery is charged by a voltage of 13-14V from the generator. If a small lead-acid battery is discharged, it will draw maybe 10-20A initially, then reducing down to about 1A. (A discharged car battery will draw maybe 70 amps for the first 10secs or so. This is why you sometimes hear the alternator belt squealing after a car engine has been started).

BUT - to charge a cellphone directly from a wind turbine, you will need a battery charger/controller system, because cellphone batteries are not lead-acid and need to be carefully conditioned and monitored to avoid over charging and over heating - including thermal runaway in some cases, depending which type of batteries you are charging.

A car lead acid battery can be charged with a simple fixed voltage source, but nicads or Li-ion types need constant current sources and very careful charging.

If you don't really know what you're doing I would be very careful - a Li-ion battery in thermal runaway is very dangerous. I would advise against experimenting.

I've got to say though, a spare charged cellphone battery in your pocket will be the smallest, lightest way of getting around your problem. The 7.2Ah battery you mention might weigh 100-200g.

OB

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