I have 3 shake lights in various sizes. I have one that will hold a charge for days. I don't know the brand. I have a small one that I keep in my EDC that I have to charge everytime I need it but I think that it gets rolled around in my bookbag and the light gets turned on. I have a larger light that I carry in my truck and I am not as pleased with it. It will hold a charge but the light is not so bright. Maybe I just need to charge it longer. If one of these does discharge completely it has to be shaken for about 3 minutes. Not so good if you need light ASAP. Except for this little problem I think they are great to have around for emergencies.