Sealed metallic enclosures, such as nuclear waste containers, often contain sensors and other electrical components which require through-barrier charging and communication. However, practicality limits interfacing through metal barriers to feed-through wires, which are undesirable due to an imperfect seal on the enclosure, and electromagnetic waves cannot be used since the systems act as a Faraday cage. Ultrasonic power transfer is thus an important alternative for powering and communicating with such systems. A typical ultrasonic power transmission (UPT) system consists of two piezoelectric transducers bonded on either side of a metallic barrier, where the transducers transmit and receive elastic waves and convert the mechanical energy into electrical energy. Such single-barrier systems have been widely studied, though the effects of self-generated heat have not been studied in detail; various sources of loss (including dielectric and mechanical losses) exist within piezoelectric transducers, which lead to self-generated heat that may affect the efficiency of the UPT system. The heat generation and effects of temperature on UPT efficiency are studied using both numerical and experimental methods. While UPT systems with piezoelectric transducers directly (and permanently) bonded to either side of a metallic barrier typically present the best performance, it is important to also consider applications which require multiple sealed metallic enclosures that are coupled in a detachable way for power and data transmission between enclosures. Due to the non-bonded nature of these multi-stage systems, a couplant (gasket) material is key for ensuring good transmission. A range of couplant materials are tested for optimizing power transmission efficiency in first a semi-detachable UPT stage, and in a completely detachable “wand” UPT stage, where attachment methods are also examined to find the most efficient and practical design for both power and data transmission.