This paper addresses the issue concerning the design of battery-powered devices. In particular, it examines aspects affecting both short-term and long-term consumption. The primary focus of the paper is a low-power device powered by miniature batteries. From a broader perspective, it can also prove useful in designing devices powered by high-performance autonomous sources. The paper first identifies the basic design requirements with an emphasis placed on the key parameters of this specific category. The following chapters describe processing and circuit measures aimed at eliminating device consumption. The concluding part sums up the findings and presents some recommendations. The described methodology for the calculation of battery life has been experimentally validated and can be used to determine the battery lifespan in virtually any system.