Since wind up flashlights are supposed to eliminate the need for a battery, some wind up flashlights have capacitors that will store the electric current you build with winding.
These types of wind up lights have a rechargeable battery inside that will store the current for a time period. A downfall of these types is that the battery tends to drain quickly, necessitating further winding.
A form of wind up flashlight is the shake light. It works on the same principle, when you shake the light up and down, friction and electricity are produced.
Good and Green
These flashlights eliminate the need to buy more batteries, considering they are contained inside the light. With fewer batteries purchase, fewer need to be produced and disposed.
A common complaint of these types of flashlights is that the light does not stay on for long, leaving the user to have to wind or shake it again to get a new charge going.
Article Written By Heather Broeker
Originally from North Carolina, Heather Broeker studied journalism and advertising at the University of North Carolina. After graduation she moved to Los Angeles, where she worked for Fox Searchlight, Fox Reality and later as a writer and marketing director. Broeker now lives in Los Angeles and runs Head Over Heels, a writing and public relations company.