A phase change material (PCM) is positioned about a battery of an eyewear device such that a latent energy of the PCM transfers to the battery as the ambient temperature drops to maintain a battery temperature. The latent energy maintains the temperature of the battery until the PCM loses it latent energy and converts to a solid phase. At normal operating temperatures, the PCM is in the liquid phase.

A semiconductor device in which a circuit and a battery are efficiently stored is provided. In the semiconductor device, a first transistor, a second transistor, and a secondary battery are provided over one substrate. A channel region of the second transistor includes an oxide semiconductor. The secondary battery includes a solid electrolyte, and can be fabricated by a semiconductor manufacturing process. The substrate may be a semiconductor substrate or a flexible substrate. The secondary battery has a function of being wirelessly charged.

A semiconductor device in which a circuit and a battery are efficiently stored is provided. In the semiconductor device, a first transistor, a second transistor, and a secondary battery are provided over one substrate. A channel region of the second transistor includes an oxide semiconductor. The secondary battery includes a solid electrolyte, and can be fabricated by a semiconductor manufacturing process. The substrate may be a semiconductor substrate or a flexible substrate. The secondary battery has a function of being wirelessly charged.

A stand-alone motor unit for use with a piece of power equipment includes a housing, an electric motor, a first fan driven by the electric motor and configured to induce an airflow through the electric motor, a power take-off shaft receiving torque from the motor, and control electronics positioned within the housing and electrically connected to the electric motor. The motor unit also includes a battery pack, and a battery receptacle coupled to the housing and engageable with the battery pack to transfer current between the battery pack and the electric motor. The motor unit further includes an auxiliary cooling system located within the housing. The auxiliary cooling system includes a heat sink coupled to the control electronics, and a second fan configured to direct an airflow across the heat sink separate from the airflow induced through the electric motor by the first fan.

Techniques for dynamically changing internal state of a battery are described herein. Generally, different battery configurations are described that enable transitions between different battery power states, such as to accommodate different battery charge and/or discharge scenarios.

Techniques for dynamically changing internal state of a battery are described herein. Generally, different battery configurations are described that enable transitions between different battery power states, such as to accommodate different battery charge and/or discharge scenarios.

A solid-state heat transporting device including a heat transporting element whose uniformity of contact with one or multiple surfaces is controllable so that various amounts of heat may be transported to and from the one or multiple surfaces. The heat transporting element uses the electrocaloric effect to absorb and release the heat and the uniformity of contact is controlled using an electrostatic effect which may change the shape of the heat transporting element. In one embodiment, the heat transporting element is an electrostatically actuated P(VDF-TrFE-CFE) polymer stack achieving a high specific cooling power of 2.8 W/g and a COP of 13 (the highest reported coefficient of performance to date) when used as a cooling device.

Provided are a battery pack configured to be easily charged even at a subzero temperature and an electronic device including the battery pack. The battery pack includes: a housing which includes a first surface including an opening and forms an exterior of the battery pack; a battery unit which is accommodated in the housing; and a heat transfer portion which is arranged on the first surface of the housing and is at least partially exposed to outside of the housing through the opening, the heat transfer portion increasing an inside temperature of the housing by receiving heat from the outside.

A battery pack includes: a plurality of secondary battery cells connected to each other in series and/or in parallel; and a housing case that includes a plurality of battery housing spaces for housing the plurality of secondary battery cells. A number of the plurality of battery housing spaces is larger than a number of the plurality of secondary battery cells. A heat absorber is disposed in the battery housing space where the secondary battery cell is not housed.

A battery pack includes: a plurality of secondary battery cells connected to each other in series and/or in parallel; and a housing case that includes a plurality of battery housing spaces for housing the plurality of secondary battery cells. A number of the plurality of battery housing spaces is larger than a number of the plurality of secondary battery cells. A heat absorber is disposed in the battery housing space where the secondary battery cell is not housed.