it can be up to 3 days If that's their optimistic estimate then I'm not sure I want to learn how long it lasts under real world conditions... Have you conside

it can be up to 3 days If that's their optimistic estimate then I'm not sure I want to learn how long it lasts under real world conditions... Have you considered adding a crank? (actually only half-joking, although I fear the machinery would not fit into such a small device)