Do you need batteries? Interestingly enough in two cases the answer is sometimes no. For well over a decade there have been electronic watches that don’t get power from batteries, but from capacitors. The movement of your arm powers a tiny generator in the watch. The generator powers the capacitor. The capacitor powers the rest of the watch. The capacitor lasts virtually forever, and there is never a need to have a button cell battery in the watched replaced. (See Electrical Storage, Present, Past and Future for an explanation of how batteries and capacitors store electricity.)
This technology has also been adapted to flashlights. The user shakes or winds the flashlight for a short time to charge a capacitor in the flashlight, which yields several minutes of light. Note, many windup lights, and other windup products such as radios, actually charge a battery not a capacitor. The distinction here is not purely academic. All batteries eventually loose their ability to hold a charge, and must be replaced. Thus products charged by winding or shaking and that use batteries, do not eliminate the generation of waste. Nevertheless, any product that avoids single use batteries at least reduces waste.
Please remember that all batteries in California, both rechargeable and single use, must be disposed or recycled as hazardous waste, they may not be placed in the trash. For information on the recycling and disposal of batteries in California, see our battery page.
Flashlights Without Batteries: A Personal Perspective
This section was first posted in 2005 and is a personal perspective of a CalRecycle staff person who avidly seeks ways to avoid single-use batteries. See Rechargeable Batteries and Chargers: A Personal Perspective.
Capacitor-powered flashlights have their limits, and in my experience, not all of them provide the duration of light claimed. Nevertheless, I find them very useful. Shaker flashlights are typically about the size of a two-D-cell flashlight. The light is dimmer than a two-D-cell flashlight, but quite adequate for finding your way though a dark house to check your circuit breaker when the lights go out, or for changing a flat tire. You could do these tasks in a rain storm if you had to because some of these flashlights are highly water resistant. My “20 minute” flashlight gives about 10 minutes of what I consider to be a useable level of brightness, and my “60 minute” flashlight gives about 15 minutes. I have seen one capacitor powered wind-up light that yields a true 20 minutes of light for one minute of winding as claimed. However, the duration of light is not always the most important factor.
Some flashlights, both capacitor and battery powered, yield a nice even beam. Others, for example, when you shine them against a wall or a floor, show a series of concentric circles or an uneven field of light, which can be annoying and less useful than a smooth, even disk of light. Additionally, the color of the light can be a factor. The light-emitting diodes (LED) that most of the shaker or wind-up lights use, and that some of the modern battery-powered lights also use, can vary in color from bluish white to blue. I find that the lights with the whiter light are more useful outdoors. If I shine a bluish light at bushes or shrubbery, the leaves, the bark, and anything nestled in with the bushes, all appear the same color, and thus are hard to distinguish. If I use a light that is whiter, I can better distinguish the colors, and thus the objects themselves. This can be useful, if for example, you are changing a flat tire at night, and accidentally kick a lug nut into the grass and leaves at the side of the road. The whiter light will be more useful to find that lug nut. However, inside your home, where objects are more familiar, the advantages of the whiter light are minimal. I have not yet found a LED light that shows color as well as flashlights with non-LED bulbs, which of course, can in most cases be powered by rechargeable batteries. See Rechargeable Batteries and Chargers, a Personal Perspective.
I keep a couple capacitor-powered flashlight in the house, and one in the car. Once when a huge tree branch fell onto a power line and took away my neighborhood’s electricity for the evening, my smallest shaker flashlight was all I needed. I could carry it in my pants pocket, I could stand it on its end to serve as a lantern, and I could see everything I needed to see both inside and outside the house. It was the perfect companion. It would be indispensable in a serious emergency.
Any flashlight that works beats a dead flashlight by a wide margin. If you tend to keep flashlights in your house or car until the batteries fail at the worst possible moment, then the advantage of capacitor-powered flashlights is obvious.