So the problem is the battery controller as suspected. It is quite a bit of effort, but I replaced the old controller board from the OE battery onto the replacement lithium cell and the watch has been working well since (last 50 days).
Attempt this at your own risk... With all battery soldering you need to be as quick as possible and you need to use solder that is designed for aluminum/tin that has an appropriate flux.
[image|2664943]
# Unwrap the black tape from the battery management controller on the original battery.
-
# Desolder the two tabs from the controller board (needs at least 350c iron temp); Make Certain to identify and mark the polarity of the battery.
+
# Desolder the two tabs from the controller board (needs at least 350c iron temp); Make Certain to identify and mark the polarity of the battery on the board.
# Repeat for the new battery and dispose of the new battery's controller pcb.
# Take precautions as to not short the battery terminals together. I keep a bucket of sand on hand in case of emergency.
# Note that the two new batteries that I had were the the opposite polarity of the OE battery, so some bending was necessary as the edge of the lipo seal which should be the bottom of the battery needs to be at the top now. I carefully folded the tabs back on themselves at the seal and then formed them into the crease where the board will sit.
# Trim the new battery leads to size.
# Tin the tabs with the special solder and then solder back to the OE controller board.
# Make sure to use kapton tape to cover the leads after soldering to ensure nothing shorts after assembly.
# Rewrap the controller board with the original tape and foam if possible. Else some 3M double-sided foam tape can be cut down and more kapton tape can be used.
Hello @Ulrich Heidenreich,
So the problem is the battery controller as suspected. It is quite a bit of effort, but I replaced the old controller board from the OE battery onto the replacement lithium cell and the watch has been working well since (last 50 days).
Attempt this at your own risk... With all battery soldering you need to be as quick as possible and you need to use solder that is designed for aluminum/tin that has an appropriate flux.
[image|2664943]
# Unwrap the black tape from the battery management controller on the original battery.
# Desolder the two tabs from the controller board (needs at least 350c iron temp); Make Certain to identify and mark the polarity of the battery.
# Repeat for the new battery and dispose of the new battery's controller pcb.
# Take precautions as to not short the battery terminals together. I keep a bucket of sand on hand in case of emergency.
# Note that the two new batteries that I had were the the opposite polarity of the OE battery, so some bending was necessary as the edge of the lipo seal which should be the bottom of the battery needs to be at the top now. I carefully folded the tabs back on themselves at the seal and then formed them into the crease where the board will sit.
# Trim the new battery leads to size.
# Tin the tabs with the special solder and then solder back to the OE controller board.
# Make sure to use kapton tape to cover the leads after soldering to ensure nothing shorts after assembly.
# Rewrap the controller board with the original tape and foam if possible. Else some 3M double-sided foam tape can be cut down and more kapton tape can be used.