The FSC-BP108 has been updated so that the battery is now replaceable.
Previously, the waterproofing was such that the beacon had to be ultrasonically sealed. A clever new twisting design allows the battery to be replaced while remaining waterproof.
Most coin cell beacons use either a CR2032 or CR2477 battery. CR2477 tend to be too large for keyfob beacons while CR2032 only last of the order of a year, depending on settings. This beacon uses an intermediate size battery, the CR3032 that more than doubles the battery life of CR2032 while keeping the size small and weight low. This beacon also uses the newer Dialog DA14531 that offers a battery life up to 6 years, depending on settings.