This is my second attempt at changing the battery on my wife's watch. The first on her Guess did not go so well. So when the time came to change the battery on her Tissot T4, it was a very stressful situation. I did not want to screw it up again.
The watch is powered by an ETA 280.002 quartz movement. This is a 2 hand movement. The movement is powered by a 321 cell.
The case back is held by 4 screws. The problem with removing the case back is that the bracelet gets in the way. I could remove the bracelet, but that is just too much work just to replace the battery. So care is the word of the day.
The case back. The gasket looks dry, so it will be lubricated before it is reinstalled.
The case back.
My local watch shop did not have the 321 cell. As such an alternate was used. Install the battery and check if the watch works. I do not have the tool to check if the quartz movement is working (for those without the second hand), so I have to wait to see if the minute hand move. Once I confirmed that it is working, time to reassemble the watch.
As normal, the screws are tightened in a 'cross' manner. This is followed by a final check by tightening the screws in a clockwise (or anti-clockwise if you like). A final cleaning and the watch is all done.