I don't think is a battery, or at least, not only the battery what is impulsing this device. <br><br>I think the manufacturer of the Oxford Electric Bell accidentally invented a Photoelectric or Thermoelectric Effect within the chemicals and the mechanical disposition used in the battery that allows the device to "recharge" every time the light, radiation or maybe other type of energy, heat or even sound itself, hits the device.<br><br><br>See, it is well known that some photoelectric effect can be produced by the proximity of two metals doped with different materials, well if the clapper between the bells is made with certain type of metal containing, I don't know...let say  Silicon that has been contaminated with the Sulfur inside of the glass, which was used to coat the battery and, eventually, the Brass of the Bells contains residues of, let say, Boron, that could mean that every time the clapper touches one of the bells there is the possibility of creating a small and instantaneous photocell that charges itself or slightly recharges the battery in presence of light.<br><br>You may think that the polarity would cause the charges to cancel each other, since the clapper also touches momentarily the opposite bell,  but, Who knows? maybe the contamination causing the photoelectric effect occurs only in the bell in one side and not in the other, or even the contamination occurs in one single side of one of the bells and, coincidentally, with the required polarity to recharge the battery.<br> <br>Although the sole photoelectric effect wouldn't recharge the battery itself, or were insufficient, due its random nature, the little amount of charge gained once in a while when the conditions coincide, may help to the extraordinary duration of the Battery.,(reply>), Have a thumbs up for sounding like someone who knows what they're talking about 😅