How long do you have to wind one of those hand-cranked battery chargers to power up a cellphone battery?
The promotional copy for many hand-crank chargers tends to use general estimates like “every minute of winding gives you two to three minutes of talk time.†Results can vary based on the fact that there are many types of cellphones and many types of batteries with different capacity ratings.
The chargers themselves can create different amounts of power when you crank them, and winding speed may factor in as well. To get a better idea of how long you have to crank to charge up your phone's battery, try visiting the manufacturer's specifications page or online manual to see if each particular hand-crank charger has more detailed information.
When shopping around, check out the product's reviews and make sure you can return it if you find it does not meet your needs. You should also check that th e charger you are interested in works with your phone, as some require cables or connections that are not included with the charger.
Chargers that use solar energy are another alternative source of power when you do not have electricity around. Some solar-energy chargers designed for specific phones do list more precise usage times, like Eton's Mobius Solar Charger for the iPhone 4, which claims one hour of solar charge supplies 25 minutes of talk time or 20 minutes of Internet use - providing the intensity of the sun is sufficient along with “other variables.â€
Be skeptical.
