Battery less than 24 hours

Same here, I charged it on 100% yesterday before sleeping and after I woke up after 8 hours of sleeping battery was drain to 36%.

Mine is draining 15% per day with about 1h of gym workout everyday. Only what I did is factory reset after update to 3.5. And the reason was that HRM sensor was not turning off when watch is charging or not on my hand. I think it was draining more before factory reset.

Just sync your watch before factory reset, reset, delete in app and under Bluetooth. Pair again and all your data is there.

I had this problem too after the first time I charged it back up after getting it. Next morning, was at 36%. Had already set the vibration low and the screen brightness to 20%.

One thing I noticed was WHILE it was charging, the music app was constantly trying to (re?)sync on its own for some unknown reason (I didn't initiate it).

So I uninstalled all the music apps (gotta delete them permanently using the ConnectIQ app), turned off the connection to my bluetooth earbuds, and recharged the watch and voila! Watch is now only using like 15-18% a day.

After a few days I put one music app back (Amazon) and synced one playlist. Just syncing the playlist took about 2 minutes but also drained about 4% battery. Just for kicks I went into the app settings on the watch and chose "sync" (would assume it just checks a hash for efficiency so it knows it doesn't need to do any work, already synced...) and it used another 3% trying to sync nothing.

At this point I'm convinced that it has something to do with the music apps trying to be smart and phoning home (syncing) when they don't need to.

Thanks, I experienced the drain issue after charging. I remembered that I added one song to my collection in Spotify. So it makes sense that it tried to sync after charging and ran into trouble. For now I deinstalled the Spotify app from my watch until Garmin comes with a new firmware update. For now the drain is solved.

I am facing a similar issue with my Garmin vivoactive 4. Bought it a week ago, I have reset it now 3 times, after the suggestions from this group, i charge it for 3 hours after reaching 100%. On the day i  charge it it is fine and drains about 1% every 2-3 hours, but the next day it starts draining by about 2% per hour. 

I am now on firmware version 3.6 and for me at least every update seems to have made the battery life worst. I am just gonna return this and get another one and hope that one is better. 

But this is preposterous to me, paying so much money i would expect a product to work out of the box and not play the guessing game of how i can make it better. Probably my last Garmin product, since this money is gone!

This watch is a mystery to me. All I can really suggest is to stick with it and eventually the battery drain problem might resolve on its own. I got my 4s in September right after it was released and now in November I am finally getting 7 days battery life. If you read my earlier posts the lightning fast drain was resolved with Garmin updates, but for the longest time I was getting 5 days life max if I let it drain completely. 

Suddenly for the past few weeks there has been noticeable improvement (after 7 days, 14% life left). I have changed nothing in the settings, it still has: stock watch face, no spotify or deezer, wrist gestures off, 20% backlight, pulse ox off, resp on. Sometimes I charge it for hours, sometimes I charge it just until it reaches 100%. I cannot make sense of this at all, but at least I am finally satisfied with the battery life.

I think some people may be experiencing shorter battery life due to watch faces that have a lot of screen updates going on constantly (like live heart rate) or, possibly, if the face just isn't coded very efficiently.

With a total of 2.5 hours of cardio activity per charge I have been getting at least 5 days of battery using the "Crystal" watch face, not showing seconds or heart rate.

That seems like a strange gamble, but happy that your watch is finally working out. I will exchange mine for another piece and hope that, that one won't have this issue