I've never had one of those crank flashlights work after more than a few hours of use. I bought several for my kids, and they didn't even make it through a weekend camping trip. I also tried keeping one in my car, and found that the second or third time I tried to use it, it would light up dimly for a few seconds after several minutes of cranking. Some component, either the capacitor or the generator, has a very high failure rate.