On my D2delta softw 5.40. I noticed from last week that my battery indicator after a full charge next day indicate 20%. And it will go down from there very slowly. It's like it's not calibrated any more.
I am sorry your battery indicator is giving bad information. With any odd behavior after a software update, there are 3 troubleshooting steps you can try. Any one of the steps may resolve the issue for your watch.
- Power your watch off then on again
- Hard reset: with your watch on, hold down the power button until it shuts off
I have had this happen a couple of times on both my D2 Delta and my wife's Fenix 5S (recently last night on the 5S) with various firmware versions. Each time I charge the watch to 100% then leave it for a bit longer. In each case the watch says 100% but within a day or so is either at a very low number or completely dead. Plugging the watch in charge eventually starts it up with 5% at which point it charges normally.
In both cases, the watches do not have any non-Garmin widgets, apps or watch faces. My D2 Delta has the default face.
What I have noted with these two units is that the watch will attempt to connect via wifi (confirmed by looking at my router) at which point it just goes into some sort of deadlock. The watch doesn't seem to connect to anything yet holds on to the IP address. It happily keeps doing this until it depletes the battery.
I do note however that you indicate that the watch does keep operating from 20%. Not sure if a hard reset is required, I find holding the power button for 10-12 seconds until it turns off then turning it back on (when you turn it back on from a forced shutdown it takes a couple of seconds to start) kills any background issue that a standard power off won't.