If you have updated the end device firmware for SmartThings devices, you may see battery drop for a couple reasons:
- Performing a firmware update involves a fair number of transmits which uses up some battery capacity
- The new device firmware reports battery differently. I believe some updates to the DTH need to be made to deal with these values properly.
Even with the new device firmware, getting a good read on battery as a percentage from a Li-Ion coin cell is a tricky problem due to the discharge characteristics of the batteries. The only real data available within the device is the battery voltage (under load and at rest) which is mostly steady through much of the battery life cycle. As an example, see the pulse load voltage characteristics for the Energizer CR2032 battery: http://data.energizer.com/pdfs/cr2032.pdf. In our tests we have seen even more dramatic voltage drops for “new” (they are never really new as they have been on the shelf for some time) batteries out of packaging.
We’ll see if we can get the DTH changes out there to provide some better (but not perfect) numbers.