battery drain

Seems like you've tried a lot of things. Here's a more complete list of troubleshooting that might help - Troubleshooting guide for high battery drain - Garmin Connect Web - Mobile Apps & Web - Garmin Forums

If still problematic suggest contacting Garmin Product Support in your region.

This just started with mine yesterday.  Charged to 100% at 3pm, down to 55% at 6am the following morning.   No activities, GPS, etc.

I just got my VenuSQ2 replaced (not repaired) under warranty. I hope this thing lasts longer than 4 months. On same settings the battery lasts on this new unit about 10 days.

I've had mine since January 2023 with no issues until now.  Today I charged to 100% and disconnected the watch from my phone so there would be no syncing, alerts, etc.  After 40 minutes I was already down to 92%.

same here, since last firmware update to 2.64, battery is draining a lot faster than before. Garmin, please fix.

Same here. For me it seems to start draining fast after charging. I restart it after disconneting from the charger and it seems to be better.

Try leaving the SQ2 connected to the charger for an extra 5 or 10 minutes after it says it's 100% charged. Not sure about the SQ2 but my VA1 and VA3 exhibited similar results. It would deplete to around 90% very quickly but would be normal after that. I think that when it says 100%, it really isn't yet.

However, based on what I've read about battery life, delaying disconnecting will likely wear the battery out quicker than disconnecting right away.

Just received a new update but nothing changed to the battery drain. I charged the device to 95% this morning. In 1 hour it went down to 85%. This is not normal behaviour. Restarting does not help.

I tried to charge over night also. No difference in battery life. Only new device fixed the problem. It must have been faulty battery or the quality of batteries on these are some cheap crap that go bad after couple of months of use.

I was able to resolve mine within a day or two.  I disconnected the watch from the phone to isolate the problem to the watch or the phone.  The battery kept draining rapidly for a while.  I did a hard reset of holding the power button for 20 sec, but upon reboot I can't say it was noticeably better, but after several hours it randomly returned to a normal battery drain of ~1% per hour.  I kept it disconnected from the phone overnight, then charged it in the morning, and reconnected to the phone.  I can't say I'm optimistic that this was the reason it returned to normal, but it's what I did.