Mag-not-so-safe power adaptor

emotistically

macrumors member
Original poster
Jul 4, 2006
39
0
I am on may macbook and I had zero battery so I plugged in my magsafe adaptor, and the adaptor is really hot. My macbook doesn't get too hot, the plug connecting my macbook to the adaptor is not hot, but the white box that you plug into the wall is burning up. It is on carpit and I am worried that it may start a fire. Does this happen to others? I thought it normally just got warm. (I had this macbook for a few weeks now)
 

mkrishnan

Moderator emeritus
Jan 9, 2004
29,777
12
Grand Rapids, MI, USA
It really depends on what you mean by hot... how soft are your emo hands? :eek: ;) :D (lol I exfoliate...I'm a softy. :eek: )

The white block in the power adaptor has the AC-DC converter etc in it. It will get hot. Just like the "wall wart" plug blocks where there is a big black plastic body on the plug end of the cable for many small electronics. But if hot means anywhwere near uncomfortable / painful to the touch, it's quite possible that there's something wrong. Although the carpet is not going to burn until far beyond painful to your touch.... ;)
 

Makosuke

macrumors 603
Aug 15, 2001
6,163
346
The Cool Part of CA, USA
Those blocks get very hot. It's a fact of life. There are occasional failures where they overheat and cause damage, but those are exceedingly rare.

Note that if it's sitting on the carpet, it's going to get hotter than it would on a more conductive surface, but what's hot to you isn't all that bad to the brick itself--it's all electric, so there's not anything in there that hates heat much, and plastic (or flooring) has a MUCH higher flashpoint than you'd think.

When I ran my MBP at max load for an hour with the brick sitting flat on the carpet, I measured its hottest point at about 55C, which is extremely hot, but I'll be still within spec.
 

mkrishnan

Moderator emeritus
Jan 9, 2004
29,777
12
Grand Rapids, MI, USA
Also just wanted to add this maybe-not-so-obvious point. When you are recharging your battery, it's like your computer is "eating for two." It's using a good ... probably 60-80% more power than it normally uses. Which means the brick gets even hotter. I just recharged my iBook and my power adaptor gets fairly warm.
 

Spanky Deluxe

macrumors 601
Mar 17, 2005
4,856
387
London, UK
My iBook's power adapter gets pretty hot. Sometimes when I use it in bed it gets under a pillow and can get *really* hot, as in "burning hot" so probably nearly 60-65 degrees celsius.
 

Xander562

macrumors 68000
Apr 2, 2006
1,628
0
When i got my first mac (MBP) i thought it was hot too, but now it doesnt seem hot at all, either it just needed to be broken in, or my nerves were stunned by the heat of my MBP :p just kidding, it doesnt get that hot. If your really fraid it will catch the carpet on fire, get a new one, just to be safe.
 

AJ's Apple

macrumors newbie
Sep 2, 2006
26
0
As well as having owned three Macs and having used them since Classic, I am also a licensed electrician and an electrical instructor.

These AC power adapters have a listing with Underwriters Laboratories in the United States as well as Canada, and bare the "c UL us" symbol. You can be assured they have been tested to high standards, and meet certain requirements. It also bares the compliance markings as required by Japan, Singapore, Europe, Norway and other standards. That being said, the nature of a power supply results in the production of heat. Therefore, use common sense when placing it on thick carpet, on or in blankets, etc.; it needs room to breath.
 

Trekkie

macrumors 6502a
Nov 13, 2002
906
16
Wake Forest, NC
emotistically said:
I am on may macbook and I had zero battery so I plugged in my magsafe adaptor, and the adaptor is really hot. My macbook doesn't get too hot, the plug connecting my macbook to the adaptor is not hot, but the white box that you plug into the wall is burning up. It is on carpit and I am worried that it may start a fire. Does this happen to others? I thought it normally just got warm. (I had this macbook for a few weeks now)
Take the wattage maximum of the adaptor times 3.421 and you get the BTU/hr that a device puts out.

I'm guessing they're 65W to 95W power adapters, if not more.

When you're charging, you're using all of it's juice to do so as it is running the charging, as well as the laptop. They get warm. Whether they're from Apple, IBM, HP, Dell, Jim Bob's Computer Hut, or wherever. They'll get warm.

If you really want to test it, find a infrared thermometer and see how warm it is. Hot to the touch <> burn the carpet hot. It takes several hundred degrees to melt carpet, and more to make it flame on. I was an idiot once and broiled some chicken in a glass dish. I decided to eat out of the dish and sat it on the carpet with nothing more than a pot holder in the center. The dish stuck to the carpet and made a nice smooth flat spot. That was probably a dish in the 300 - 500 degree range. No flames.
 

Sesshi

macrumors G3
Jun 3, 2006
8,113
1
One Nation Under Gordon
YS2003 said:
I think you should be able to sell that design to Dell:) . I think it blends in their model line up.
No need. My Inspiron PSU runs pretty cool in comparison to the furnace-like MB/MBP PSU's. No other manufacturer's laptop PSU's has ever caused me as much concern as the Apples in terms of heat (and in the case of the MBP, reliability).
 

0098386

Suspended
Jan 18, 2005
21,576
2,887
Sesshi said:
What? Apple PSU's get unfeasibly hot? You don't say...

I should patent this :p
Too late daddio! The earliest Pentium 4 laptops had fans in the power bricks, at least the ones that were dotted around college.

My PSU doesn't get that hot. I mean it gets warm but never dangerously, never enough to cause any damage. At the moment mine is as warm as a cat.
 

Sesshi

macrumors G3
Jun 3, 2006
8,113
1
One Nation Under Gordon
Mine's (third after two went out in short order) not been bad. It's just quite warm now (Although the Sony I have beside it is actually cool). Maybe it's just the 'hunka hunka burning Apple'* ones which go out. Ooer... watch out, OP! :D




* Apologies for stupid Elvis reference