Had a failure of a Di2 battery. Would charge ok, then lose charge overnight. Replaced the battery, it was 6 years old, same issue. Took to a LBS they said shifter (1x system) was bad. It would shift but showed an issue in the shop test software. I sourced a replacement XT Di2 shifter from Jenson for $90. I was still able to ride while I awaited the new shifter as I simply unplugged the shifter cable after use, saved the battery,