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acts4:12

macrumors member
Original poster
Nov 22, 2016
53
73
Hey guys, I have a Cellular S6 on the latest 7.4 Beta. It is connected to an 11 Pro Max.

I have noticed massive battery drain at night. Like sometimes 50% in a regular 7 or 8 hr sleep session. The strange thing is, during the day the battery lasts like a champ and seems to do extremely well. It seems like there is something during the night that is causing excessive drain.

I do use the "Sleep" function at night. I do wear my watch somewhat loosely, so i'm wondering if possibly the Blood Oxygen or heartrate sensor keeps running because it's not getting a good reading? What do you guys think? Anyone else experiencing this?
 

G5isAlive

Contributor
Aug 28, 2003
2,458
4,243
I would suggest you do the experiment.. don't use the sleep function but put the watch next to the bed. My guess is your power drain will vanish. And I do think you are right, the sensors which project light are likely to be struggling. I dont have experience with sleep. How is the phone signal in your area. the thing I have noticed is batteries tend to drain faster in areas of weak signal. perhaps your bedroom is shielded? grasping at straws sorry.
 

acts4:12

macrumors member
Original poster
Nov 22, 2016
53
73
I would suggest you do the experiment.. don't use the sleep function but put the watch next to the bed. My guess is your power drain will vanish. And I do think you are right, the sensors which project light are likely to be struggling. I dont have experience with sleep. How is the phone signal in your area. the thing I have noticed is batteries tend to drain faster in areas of weak signal. perhaps your bedroom is shielded? grasping at straws sorry.
Thanks much for the reply. I appreciate it. Yeah, i'm going to have to try not using it and see what happens. I don't think it's related to the cell signal as I'm always on WiFi at home. I'll try tonight a couple of things and report back.
 

waw74

macrumors 601
May 27, 2008
4,664
938
I don't think it's related to the cell signal as I'm always on WiFi at home.
if your phone is close, the watch is on bluetooth to the phone, And the watches wifi and cell radios are powered off.
so low cell signal would cause power drain on your phone, but little to no difference on your watch. (and if your phone has good wifi, then the cell shouldn't eat too much of the phone's battery.)

But if your phone is out of BT range while you sleep (or if your phone is off or in airplane mode), then the watch's wifi radio will come on, which uses more power than the BT.
then if the watch can't find wifi, it will power on the cell radio.

If it doesn't bother you too much, you could try a night or 2 with the watch band a little tighter.


If you go into the health app on your phone, and select "show all data" towards the bottom, you should be able to see each heart rate/Ox reading, and the time it was taken. I don't know how often it should update, but you should see a pattern of "every 10 minutes" or something similar. Compare that on different nights with how tight the band is, If the time between changes dramatically, then it's probably the sensors repeatedly trying and failing that's eating your battery.

I have a S5, so no Ox, and I don't use apple's sleep, so I can't help with what the timing should be.
maybe others can.
 

perezr10

macrumors 68000
Jan 12, 2014
1,990
1,456
Monroe, Louisiana
I’m not sure about your specific night time issue. But the blood oxygen function is a known big battery user. I’ve been watching YouTube battery tests that show the SE gets better battery life than the 6 unless you turn off blood oxygen testing.
 
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