Watch stays warm when 100% charged, didn't used to

sprucemoose

macrumors member
Original poster
Jun 26, 2015
48
21
I've had the watch for nearly two weeks now, and I charge it every night with the supplied charger, no stand, and yes I've taken all the plastic wrapping off.

For the first two weeks, my watch was always nice and cool when at 100% charge, just like my iPhone or iPad. Since last night, it now stays warm even after it's reached 100%, no matter how long I continue to leave it on the charger.

Has anyone else experienced this? It still seems to be charging fine. The charger and watch both cool down when disconnected. A reboot or putting it in airplane mode didn't fix it. My watch shipped with OS 1.0.1.

Not sure if anything is wrong here with the charger or watch. Normally it wouldn't seem too suspicious, it's just that it didn't behave this way until now.
 

sprucemoose

macrumors member
Original poster
Jun 26, 2015
48
21
No ill effects otherwise? I noticed some people had their chargers replaced and that helped, but in addition to warmth they also experienced no charging or a message on the watch that the accessory could not be used.
 

melman101

macrumors 68030
Sep 3, 2009
2,692
271
No ill effects otherwise? I noticed some people had their chargers replaced and that helped, but in addition to warmth they also experienced no charging or a message on the watch that the accessory could not be used.
Are you using a stand? Make sure the charger is fully connected to the watch.

But no ill effects.
 

papbot

macrumors 6502a
May 19, 2015
513
134
I've had the watch for nearly two weeks now, and I charge it every night with the supplied charger, no stand, and yes I've taken all the plastic wrapping off.

For the first two weeks, my watch was always nice and cool when at 100% charge, just like my iPhone or iPad. Since last night, it now stays warm even after it's reached 100%, no matter how long I continue to leave it on the charger.

Has anyone else experienced this? It still seems to be charging fine. The charger and watch both cool down when disconnected. A reboot or putting it in airplane mode didn't fix it. My watch shipped with OS 1.0.1.

Not sure if anything is wrong here with the charger or watch. Normally it wouldn't seem too suspicious, it's just that it didn't behave this way until now.
Mine has been warm every day since I got it over a month ago when I remove it from the charger. It's normal as far as I can tell.
 

sprucemoose

macrumors member
Original poster
Jun 26, 2015
48
21
One other question: is your charging puck warm when it's not connected to the watch? Mine feels lukewarm when not connected. If I unplug it from the wall, it becomes cool.
 

Aluminum213

macrumors 68040
Mar 16, 2012
3,413
3,505
sometimes warm sometimes cold, makes no difference


unless something goes wrong with the watch I wouldn't worry, if it did Apple would replace it no questions asked
 

Andydigital

macrumors regular
Feb 9, 2013
171
24
It only takes about 2 hours to charge and when it gets to 100% it stops charging altogether, so over night it has time to discharge enough that it needs to charge again to top back up to 100%. The way inductive charging works means that the puck gets quite warm in the process, that heat takes a bit of time to dissipate, so some mornings you may just happen to pick it up just after it finished topping up and some other morning you may not. Yesterday for example when I picked mine up it was at 99% even though it had been on the dock all night, I obviously caught it between top up cycles.
 

sprucemoose

macrumors member
Original poster
Jun 26, 2015
48
21
It only takes about 2 hours to charge and when it gets to 100% it stops charging altogether, so over night it has time to discharge enough that it needs to charge again to top back up to 100%. The way inductive charging works means that the puck gets quite warm in the process, that heat takes a bit of time to dissipate, so some mornings you may just happen to pick it up just after it finished topping up and some other morning you may not. Yesterday for example when I picked mine up it was at 99% even though it had been on the dock all night, I obviously caught it between top up cycles.
The weird thing is that I put it back on the charger at 100% and left it a while, maybe 30 mins, and it just wasn't cooling down. Later that night I tried it again, and the watch did cool down soon after reaching 100%.

I hope you're right and I'm just missing something here, but it felt like I gave it plenty of time.

The other possibility that came to mind is a software bug where sometimes the watch just doesn't stop drawing power when it's finished. The battery stops accepting the charge and so it all just converts to heat around the puck. Not sure if that makes sense.
 

Andydigital

macrumors regular
Feb 9, 2013
171
24
As far as I understand it, 100% written on the GUI (screen) on apple devices isn't really 100%, there is usually about 5-10% more headroom in the battery before it's truly 100% full. This design decision is so that people don't unnecessarily worry when their device no longer shows 100% after as little as a few months of ownership. If they showed you the true battery state some users could see their max battery capacity be as low as 90% even after as little as a year, it all depends on how much people use their devices each day. So this extra headroom helps reduce support enquiries and returns requests.
 

sprucemoose

macrumors member
Original poster
Jun 26, 2015
48
21
As far as I understand it, 100% written on the GUI (screen) on apple devices isn't really 100%, there is usually about 5-10% more headroom in the battery before it's truly 100% full. This design decision is so that people don't unnecessarily worry when their device no longer shows 100% after as little as a few months of ownership. If they showed you the true battery state some users could see their max battery capacity be as low as 90% even after as little as a year, it all depends on how much people use their devices each day. So this extra headroom helps reduce support enquiries and returns requests.
Thanks. Next time this happens I'll keep it on the charger for a couple of hours, checking the watch periodically, just to make sure there's nothing suspicious going on. I'll let you know what I find.
 

sprucemoose

macrumors member
Original poster
Jun 26, 2015
48
21
It only takes about 2 hours to charge and when it gets to 100% it stops charging altogether, so over night it has time to discharge enough that it needs to charge again to top back up to 100%. The way inductive charging works means that the puck gets quite warm in the process, that heat takes a bit of time to dissipate, so some mornings you may just happen to pick it up just after it finished topping up and some other morning you may not. Yesterday for example when I picked mine up it was at 99% even though it had been on the dock all night, I obviously caught it between top up cycles.
On further testing I believe you're right. Apple claims the watch takes 1.5 hours to charge to 80% and 2.5 hours to charge to 100%. We can also assume that final 20% is not linear, meaning the watch takes longer to charge as it reaches full capacity. In my testing, the watch continued being warm for about 30 minutes after showing 100% but did eventually cool down. Disconnecting it from the charger and leaving it for a few hours dropped the battery a few percentage points, backing up your explanation that the charger kicks in a few times throughout the course of a night.

The difference between the watch and the phone seems to be all about the inductive charging. When the phone is between 95-100% it cools right down while it's trickle charging, so it's always cool in the morning. But the watch's charger gets hot even during that last 5%.