The second link isn't exactly forthcoming on the battery technology used, but at least says: > and its power consumption is low enough that the device can last

The second link isn't exactly forthcoming on the battery technology used, but at least says: > and its power consumption is low enough that the device can last from six months to a year on a battery of the equivalent size The average "width" of the first mandibular molar from this article[1] is 5.1-5.2mm. It sure would be interesting to see a CAD model of the design inside the module on the band. The graphics from the posted article vs. the first link above are also a bit different, making it even harder to infer much I think. [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC5502574/ https://pmc.ncbi.nlm.nih.gov/articles/PMC5502574/