The ultra-thin, cm scale SSB 250µAh, Stereax M250 contains no liquid or polymer components and, like all Ilika solid state batteries, has no free lithium, either in the charged or discharged state, making it moisture resistant and appropriate for medical applications. Its low self-discharge allows it to be trickle-charged by an energy harvesting source such as vibration or a PV panel. Its high peak current enables the transmission of data using protocols such as Bluetooth Low Energy. The combination of energy harvester, transmitter, sensor and the M250, is ideal for integration into small, “fit and forget” autonomous sensor devices with multiple applications. This includes the Internet of things (IoT) sensors for smart homes & cities, vehicles and medical devices. The M250 is provided on a rigid substrate (650µm), though thinner substrates may also be used.