vertsix

macrumors 65816
Original poster
Aug 12, 2015
1,249
1,970
Usually when I remove my Apple Watch from the inductive charger in the morning, it is usually fairly warm or hot.

This doesn't happen all the time, but most of the time. It's strange. I don't recall older iPhones doing this.

Anyone else?
 

exxxviii

macrumors 65816
May 20, 2015
1,423
555
Normal for me. I would rate it very warm, but not hot. Every device I have ever owned gets warm to hot when it charges. I suspect that the AW is warmer than some, because the inductive interface is less efficient than a direct wire connection (transformers get very hot, and the induction link is effectively a transformer).
 

nburwell

macrumors 603
May 6, 2008
5,047
1,952
DE
I have noticed that my AW has been warm on several occasions (none recently that I can remember). But its never been hot though.
 

Newtons Apple

Suspended
Mar 12, 2014
22,757
15,235
Jacksonville, Florida
Normal for me. I would rate it very warm, but not hot. Every device I have ever owned gets warm to hot when it charges. I suspect that the AW is warmer than some, because the inductive interface is less efficient than a direct wire connection (transformers get very hot, and the induction link is effectively a transformer).

I got to wonder as both iPhone and AW go on the charger before sleep and both should be fully charged within an hour or so. My watch is warm, even though it has to done charging hours ago, why would it still be warm. My iPhone is NEVER warm.
 
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exxxviii

macrumors 65816
May 20, 2015
1,423
555
My watch is warm, even though it has to done charging hours ago, why would it still be warm.
Probably due to the inefficiency in the inductive loops inside the watch. Those loops are energized, regardless of whether the watch is using the power.
 

sean000

macrumors 68000
Jul 16, 2015
1,623
2,343
Bellingham, WA
I've noticed mine seems to be warmest if I take it off while it is actively charging. Most mornings I am taking it off hours after it should have reached 100% and on most mornings it doesn't feel warm to me at all. I have never felt it get truly hot.

The warmest watches I have felt were in the Apple Store while I was trying them on last year. These were watches that spent all day (and night) on the chargers, except for brief try-ons, and they were also closed up inside of a drawer while charging.

Sean
 

BarracksSi

Suspended
Jul 14, 2015
3,902
2,662
I've noticed mine seems to be warmest if I take it off while it is actively charging. Most mornings I am taking it off hours after it should have reached 100% and on most mornings it doesn't feel warm to me at all. I have never felt it get truly hot.
Same here. I wear mine into bed, which means it usually doesn't charge overnight, but I leave it on the charger long enough to go from 40%-ish up to 100%. If I pull it off the charger while it's charging or soon after it hits 100%, it's pretty warm. But if I wait longer (maybe an hour, I'm guessing) and then pull it off the charger, it's cooled down, almost back to normal.
 

Julien

macrumors G4
Jun 30, 2007
11,545
4,721
Atlanta
I'm so frightened of scalding my arm or melting the ceramic back that I charge mine in the freezer. :D
 

Julien

macrumors G4
Jun 30, 2007
11,545
4,721
Atlanta
Newsflash: In the morning the batteries should have been charged hours ago so the charging is over and the heat must be coming from the induction coils
When the charge drops a few percent (the device is on and using current) it will start charging again and 'top off' and charge again. This will likely happen several times during the course of being on the charger for 8 hours. Also the last 10% (90% to 100%) of a lit-ion's charge is done at the slowest rate and will produce the most waste heat.
 
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Newtons Apple

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Mar 12, 2014
22,757
15,235
Jacksonville, Florida
When the charge drops a few percent (the device is on and using current) it will start charging again and 'top off' and charge again. This will likely happen several times during the course of being on the charger for 8 hours. Also the last 10% (90% to 100%) of a lit-ion's charge is done at the slowest rate and will produce the most waste heat.

Not so sure about this happening several times during 8 hours on the charger. The AW is in sleep mode, doing very little while on the charger and having to top it off several times while on the the charger for 8 hours does not seem right.
 
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Julien

macrumors G4
Jun 30, 2007
11,545
4,721
Atlanta
I am surprised that some of the people worried about saving our resources have not complained about how inefficient wireless charging is.

An average cell phone only uses about 3 kWh to 4 kWh of electricity per year. An :apple:Watch would like use about ¼ to ⅛ of this even accounting for the approximate 25% loss in efficiency of inductive charging. So the 25% loss would be probably be around 10¢ to 30¢ of electricity costs per year.
 

Newtons Apple

Suspended
Mar 12, 2014
22,757
15,235
Jacksonville, Florida
An average cell phone only uses about 3 kWh to 4 kWh of electricity per year. An :apple:Watch would like use about ¼ to ⅛ of this even accounting for the approximate 25% loss in efficiency of inductive charging. So the 25% loss would be probably be around 10¢ to 30¢ of electricity costs per year.

But when you multiply that by all the iPhones . . . . well that would not fill my 300 gallon diesel tank on my Luhrs!
 
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BSben

macrumors 65816
May 16, 2012
1,114
577
UK
Mine got quite hot once, almost a year ago, on that morning it developed some other problems too (no sounds or taptic feedback and other things). Ended up un-pairing and re-pairing which solved the issue.
 

joeblough

macrumors 6502
Sep 30, 2006
461
280
old thread, but i can say this: having inherited 2 S0 apple watches, one stainless and one aluminum, the stainless one is warm as long as it is on the charger (i'm talking 12-24 hours after attaching it to the puck). the aluminum one is always cool to the touch when it's done charging (here talking about 8 hours after starting to charge.)

something is definitely funny. i don't think you can just lump this under "inductive charging causes heat"...
 

Archer1440

Suspended
Mar 10, 2012
730
301
USA
I have three Apple watches, a 0, 2, and 3LTE. All of them are variable from room temperature to slightly warm after sitting on their chargers, often different from one day to another, and I’ve always thought that was probably connected to whether they were updating music playlists or other content while sitting.
 

orev

macrumors 6502
Apr 22, 2015
466
830
Probably due to the inefficiency in the inductive loops inside the watch. Those loops are energized, regardless of whether the watch is using the power.
Loops are not energized if not charging. That's part of the technology of wireless charging -- how to shut it off when power is not needed.
 

joeblough

macrumors 6502
Sep 30, 2006
461
280
I have three Apple watches, a 0, 2, and 3LTE. All of them are variable from room temperature to slightly warm after sitting on their chargers, often different from one day to another, and I’ve always thought that was probably connected to whether they were updating music playlists or other content while sitting.

interesting. in my case the watch being charged is disconnected from the phone, but of course it is on wifi. i don't think it has anything to update as it has only 1 app loaded and i have never added any playlists to it.
 
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