In the last few years a number of different companies have started selling flashlights that don’t require batteries – perfect for use in hurricanes, tornadoes, or other emergency situations where you don’t want to worry about rummaging through the junk drawer. To the best of my knowledge these flashlights come in two basic varieties: one that you shake and another with a hand crank you can turn. Either way, there’s a tiny generator inside the flashlight that uses the motion as a power source. Shaking or cranking for one minute gives you something like a half-hour’s worth of light.
My idea is to implement a similar self-powering technique for mobile phones. I think most mobile phone users have had the experience of being stranded without their phone charger (or a power source, for that matter) when their phones died. Now that wouldn’t be an issue. Just give the phone a vigorous shake for a minute or two and you won’t need to worry about missing calls. Other people on this site suggested solar-powered cell phones, but the advantage of motion power is that you don’t have to wait very long to use your phone again (and you aren’t dependent on the whims of the weather).
This could also be a great way to spread mobile phone use in parts of the third world where electricity isn’t readily available. If a wireless company and/or government agency would be willing and able to put up a few phone towers, villagers in the middle of nowhere could be in touch with the rest of the world even without any electricity, roads or any other infrastructure. It could be a huge quality-of-life improvement for the rural poor, especially if they have friends or family in distant areas that they don’t get to talk to very often.
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The reason the shake light appeared only recently is because it only became practical after the development of high efficiency LED flashlights. The LED uses very little power, which is what makes it practical. A cell phone uses a lot more power than an LED flashlight. This is because it has to have a radio transmitter capable of generating a powerful enough signal to communicate with a cell tower that may be miles away. To generate enough power to charge a cell phone battery, you would need a hand-cranked device of considerable size and you would have to crank it for a long time. This is possible, and for people out in the boonies this might be an option, but the generator would probably be inconvenient to carry and most people wouldn't want to have to crank it as much as would be necessary.
As long as this feature didn't make the phones too big (think Zack Morris's phone from Saved By The Bell), this idea might fly in the developed world. But right now, I think that the developed world is too attached to the sleak, thin phones for this to work.
FWIW, I have one of those crank flashlights that has an accessory set to charge some cell-phones, in an emergency fashion.
And if shaking phones proved to be impractical as a means of generating power, then perhaps a small handcrank could come with the phone that could attach to the side of the phone generating power in ways similar to the handcrank flashlight.
This is a great idea - particularly since cells phone manufacturers haven't agreed upon a universal charger, meaning that when your battery dies the task of recharging it is more difficult than necessary.
To integrate this into the phone would make them very large and heavy. However, if you made an external charger (some are already available integrated in emergency radios) with universal adapters, it would provide the same function without the blowback of added weight.
There are products on the market for emergency cell-phone charging (search "hand crank phone charger" and you get sites like http://www.soscharger.net among others) using hand cranks, but nothing, it seems, that is built-in to the phone. The size issue is a major one, at least with the technology now. My guess is that the only market for this would be in developing countries where single-person phone ownership is not the norm and compact size isn't an important feature. For consumers who carry their own phone everywhere, it would need to be a removable attachment.
I agree it is a good idea as long as the size can be kept down.
Would be great if cell phones worked the way my watch did. I have a Casio G-shock that has small solar panels built around the LCD display and it's hooked up to the primary battery. Just a couple minutes in the sunlight will charge it for weeks.
(P.s. I highly recommend this watch. Solar-powered, atomic-clock updated 3 times a day, automatically detects low light conditions and when you hold the watch up to turn on the light)
With current stepping power supply technologies, there is no reason that a cell phone can not have a small flip plug to plug the phone directly into an outlet. The large transformers are a lazy engineers method of readily getting the charging voltage and current desired.
A tiny circuit can monitor house current and RF modulate the switching characteristics of the plug voltage to create an effective DC current for charging the Li-ion battery.
The concept is to send the current from the plug down multiple paths, each path with different propagation delays. The composite signal would be a largely DC current.
If the plug is made to be part of the phone, you won't forget the charger.
If you are out backpacking and need to charge the phone. A solar panel is a nice lightweight option that could double for running your radio and other electronic equipment.
Solar Charger: At the equator, the Sun provides approximately 1 kilowatt of power per square meter (~10 sq ft). I haven't investigated the power available with increasing lattitude. So if a solar cell is 40% efficient, that is 400 watts at the equator. Assuming a 20 Volt solar cell setup, that would be approximately 20 amps. Since a charger only needs about 2 amps at 12 volts or less, the size of the solar cell needed would be around 100 sq centimeters (~16 sq inches) or about 4" x 4". Certainly small enough to carry. This could be folded to reduce the stored dimensions.
Just what we do not need --here you are driving down the road shacking your phone trying to charge it enough to get it to work--all the time weaving all over the road. I have a cell phone myself---I want the use of the cell phone while driving to be like the DWI because both are as bad as the other!! Drive down any road and watch the weavers talking on the cell phone,That is MULTI TASKING!!
My cell phone uses a 5V adapter, it should be very simple to make an adapter from a "shake light." The problem is that the "shake light" stores energy in capacitors, while the cellphone has a lithium battery pack; somehow, the capacitors would have to discharge very slowly into the cell phone's battery pack. While sixty seconds of shaking may provide 20 minutes of LED light, I suspect it would supply only a few seconds of cellphone use. Maybe that would help in an emergency, but I personally keep a cigarette lighter cellphone charging cord in the car next to the "shake light," which is supplemented by my keychain LED light and my LED-equipped house key, I've also got a spare battery pack for the cellphone...
The problem with this is that if you shake the shit out of your cell phone for long enough it may break. Think of all the legal troubles too. "But you told me I had to power it by shaking it... and it was raining... and my phone got embedded in my son's skull." It's just not a pretty picture.
How about instead of the phone being self-powering, have a hand wound charger or quick changer. There are radios that use this as a power source, wind up a coil spring to maintain a constant voltage output to be used as a charge point. It may take several times to wind up to fully charge a phone, but it's a lot better than nothing at all.