New MBP 15" became insanely hot during charing running a few programs.

[nph]

This morning I had discharged my 2017 MBP 15" base model down to 40% running Windows 7 in Vbox and a few office apps+ Skype. I put it on the bed and connected the charger. Came back with my coffee after 10 minutes and the machine was really hot on the bottom center! Scary hot.
I took it off the bed and placed it on my knees but I had to avoid the center since I couldn't have it touch my skin. My old 2013 MBA with the same apps running while charging never got this hot!
I then started a Skype session, audio only and went on with it for 30 minutes. Despite sitting with air underneath and not really starting any windows programs in Vbox etc but just checking email and doing a Skype call it didn't cool down until it had recharged completely.
So I stopped at a Best Buy and ran the dev null tes command starting 4 processes on a 13" and 8 on the 15". Let the battery go down 10% while I ran some apps like FCPX and Garageband and iTunes playing songs.
After 15 minutes I reconnected the chargers and none of them (15" was actually a 2016 model) got any hot at all, barely warm underneath.
Btw,my CPU never went beyond 40% as far as I could see from Activity Monitor while the two machines at Best Buy were at 100% CPU usage while i was testing them.

Now this has me worried. Could there be something wrong with the battery/charge mechanism in my MBP?
I have scheduled a Genius appointment at the end of the week and I am still in my 2 week return period but would prefer not to have to replace it since I think the keyboard is great. No stuck keys even though it ran this hot for 30 minutes so it passed that test real good!

Has anyone else felt such heat from underneath their MBP while charging?

 

[killawat]

I put it on the bed and connected the charger.

Voltage from battery charging and CPU utilization + blocked vents = heat.

Your 2017 MBP has two extra cores and requires twice the wattage to run. (at max)

edit: twice

 

[nph]

So with the same load the 15 will be more hot than the 13?

 

[keysofanxiety]

So with the same load the 15 will be more hot than the 13?

Depends what the load is. But the dGPUs will kick in under editing which will run a lot hotter.

It's also important to remember that the system may feel extremely hot to the touch, but that doesn't necessarily mean the internal components are cooking themselves as the aluminium enclosure is partly used to displace heat.

 

[nph]

So my question then is would the 13" TB with i5 processor run equally hot as my 15"?
If anything I thought the i7 wouldn't have to work as hard so it would be cooler...
Would i be better off with i5 then? The heat generated was hot en ought I couldn't have it touch my skin so uncomfortable. I like more power but if the 15" will generate a lot more heat than my macbook air without feelsing much faster then I might as well go with the 13" or?
I don't mind some heat but not like this.

 

[jerryk]

Where are the are intakes located on the unit? On my 2015 15" there are underneath the unit so putting it on a bed could have blocked them.

 

[leman]

Where are the are intakes located on the unit? On my 2015 15" there are underneath the unit so putting it on a bed could have blocked them.

That would also be my guess. Putting the 2016+ model on a soft blanket is very likely to block the air intake, even more so than with the 2015 models.

 

[KGB7]

You didn't mention if the fans were running once the Mac was on your lap. If you didn't hear the fans or couldn't feel the air coming out, than you have a problem.

 

[nph]

So now that I think about it the fans didn't sound too loud and eve though the airflow might have been blocked on the bed it sure wasn't on may lap. Also I had it like that for 20 minutes and it didn't cool down until charging was complete.
I think I will try and repeat the experience today and see what happens since I have Fanny installed which will tell me the temp and fan speed.

 

[New_Mac_Smell]

So now that I think about it the fans didn't sound too loud and eve though the airflow might have been blocked on the bed it sure wasn't on may lap. Also I had it like that for 20 minutes and it didn't cool down until charging was complete.
I think I will try and repeat the experience today and see what happens since I have Fanny installed which will tell me the temp and fan speed.

Excuse me, there's an app called "Fanny"? I hope that's a typo, otherwise that's blooming hilarious! (Maybe not to US, but native English speaker be laughing).

Honestly if you block the air intake the computer will get hot, it's just basic physics. It needs airflow, there's no point repeating as it'll just do the same thing again. When charging/discharging it's pushing more energy through the system, energy/heat are the same thing.

 

[KGB7]

Excuse me, there's an app called "Fanny"? I hope that's a typo, otherwise that's blooming hilarious! (Maybe not to US, but native English speaker be laughing).

Honestly if you block the air intake the computer will get hot, it's just basic physics. It needs airflow, there's no point repeating as it'll just do the same thing again. When charging/discharging it's pushing more energy through the system, energy/heat are the same thing.

It shouldn't get that hot. I've never seen such issue from normal use and it shouldn't be an issue unless there is a problem.

 

[New_Mac_Smell]

It shouldn't get that hot. I've never seen such issue from normal use and it shouldn't be an issue unless there is a problem.

I didn't see any temperatures though so thought it was purely subjective? The OP mentioned it was so hot they couldn't rest it on their bare skin, but honestly it doesn't need to be that hot to cause a level of discomfort.

 

[nph]

Note the MBP was only on my bed for a few minutes and in my lap with free airflow for 30 minutes and still extremely hot.
I just tried again and it didn't get quite as hot but interestingly enough the fans did not spin up even when processor temp went to 129F (from running normally 30-40C it went to mid 50s C) so from roughly 100F to 120 and fan speed did not change. Is that normal?