An apparatus including a proton battery and a casing for the proton battery, the proton battery including first and second electrodes configured to form an electrode junction configured to generate protons in the presence of water to produce a potential difference, the proton battery further including respective charge collectors in contact with the first and second electrodes; the casing configured to inhibit exposure of the electrode junction to water from the surrounding environment when the proton battery is contained within the casing, the casing including a pair of electrical terminals electrically connected to the respective charge collectors of the proton battery, wherein the proton battery is formed as a continuous strip of material, and wherein the casing includes an opening configured to enable a length of the continuous strip to be extracted from the casing.