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Author Topic: Why is my laptop so hot when plugged in, but cooler running on batteries?  (Read 35916 times)

Offline Carolyn

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When my laptop is plugged in it burns my legs, but almost as soon as it's unplugged it starts cooling down.  How come?

[MOD EDIT - PLEASE FORMAT YOUR POST TITLES AS QUESTIONS, CAROLYN. THANKS. CHRIS.]
« Last Edit: 15/12/2009 09:11:22 by chris »


 

Offline that mad man

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A by-product of the battery charging is heat, it happens to all batteries that are on charge. When disconnected the laptop is working off the battery power only, so its much cooler.

Unfortunately the worse place to have a laptop is...... on you're lap!

The air vents that keep things cool are mainly on the bottom so when its on the lap some of the air vents can get covered. This causes overheating and can shorten the life of the battery and components.

I use a tea-tray that has a beanbag style bottom thats comfortable and sits well on the lap. It cost me £5 from a supermarket and is normally used for TV dinners etc.

Well worth the cost.


 

Offline Karen W.

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I have one of the bean bag tea trays and it works great for my keyboard also.
I don't have a lap top at the moment so I also use it for my phone which has a stand and I post from there too. The table helps with that too. even though my phone is a mini laptop, sort of it gets hot if I hold it long while on the internet and over heats so if I stand it on its stand on a laptop table it sits at the angle of a tent and is easily used that way! Does not overheat the battery like a laptop then!
 

Offline JimBob

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My Nephew has a new computer with a cooling platform - two fans. BUT it was not doing as advertised so he had a friend make a 3/8 inch aluminum plate to fit underneath it with slots 1/4 inch away and radiating from the reduced diameter of the fan holes. Works like a charm. Keeps the computer cool. Heat is one of the main reason computers become damaged.
 

Offline m.saffered

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When my laptop is plugged in it burns my legs, but almost as soon as it's unplugged it starts cooling down.  How come?
yeah.....i have been experience of this.....i don't know the exact reason behind this but may be there's isn't much heavier cooling system compare to desktop fans (at list)...!!
 

Offline JoanJoan

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My old laptop used to continually overheat and shut itself down.  I eventually replaced it and my new one works perfectly.  I've had my current laptop for about two years but the battery life is very short.  Even when I switch it to the "power saver" setting, I don't get more than an hour from it.  Does anyone know what affects the battery life and what you can do to look after the battery?
 

nixietube

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Does anyone know what affects the battery life and what you can do to look after the battery?

Lithium based:   Heat will reduce the life of the battery.

NiMH:  Over-charging will do the job here. Let the battery fully discharge from time to time. Charging circuits vary in quality, so as a general rule take it off charge when fully charged.


 

Offline LeeE

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Nearly all laptops will run at a lower speed when running on batteries to reduce the energy requirements and to achieve a usable battery run-time.  If the laptop has a multi-core processor it may even shut down one or more of its cores.

Compare the cpu frequency between running on mains power and batteries.  For example, my old P3 based vaio will run at 750MHz on mains power but drops to 550MHz when on batteries.

The drop in heat is just a consequence of these power saving measures; obviously, if your laptop was as hot on batteries as when on mains power, much of your battery power would be just being turned into heat.
 

Offline m.saffered

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Does anyone know what affects the battery life and what you can do to look after the battery?

Lithium based:   Heat will reduce the life of the battery.

NiMH:  Over-charging will do the job here. Let the battery fully discharge from time to time. Charging circuits vary in quality, so as a general rule take it off charge when fully charged.




yeah, that's fine......but if we directly used the supply from mains for the whole working duration than would it be affected the battery life....?
 

Offline m.saffered

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Hey LeeE, as per your clauses like "If the laptop has a multi-core processor it may even shut down one or more of its cores" , than my question here is, if this phenomena occur than it mean we have the facilities of dual to tetra Cores but we can't use it.....?
 

nixietube

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Does anyone know what affects the battery life and what you can do to look after the battery?

Lithium based:   Heat will reduce the life of the battery.

NiMH:  Over-charging will do the job here. Let the battery fully discharge from time to time. Charging circuits vary in quality, so as a general rule take it off charge when fully charged.




yeah, that's fine......but if we directly used the supply from mains for the whole working duration than would it be affected the battery life....?

Leaving circuit faults or  poor design to one side:


Lithium based makes no difference plugged in or not. My laptops remain plugged in to the mains power when it is available. The critical factor is temperature, in storage or in use. A perfect example is all the hand wringing over the iPhone battery. I have an iPhone ( and I LOVE it).. but look how it is stored.. in thigh pocket, in a coat pocket, on the dashboard in the sun ( in the UK this is not a factor - sadly :(  )...

So the answer to your question is no.


NiMH: Here you would need to look into exact details of the charging circuit. I haven't seen many NiMH laptops nowadays so I'll not go into details unless you want me to.

So the answer to your question here is  - it depends. Most likely - yes.
« Last Edit: 16/12/2009 00:32:43 by nixietube »
 

Offline LeeE

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Hey LeeE, as per your clauses like "If the laptop has a multi-core processor it may even shut down one or more of its cores" , than my question here is, if this phenomena occur than it mean we have the facilities of dual to tetra Cores but we can't use it.....?

Not on batteries.  Instead of getting perhaps two hours on a charge, with cores shut down and reduced CPU frequencies, you'd just get 15-20 minutes running time.  Check your specific model specs to find exactly what power saving strategies it uses and how long it's supposed to run for on batteries.  Then charge it up and see if you anywhere close to the claimed battery run-time while you're actually doing any useful work.
 

Offline JP

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You can usually change your power saving settings.  If I'm trying to run something that requires a lot of computing power while I'm taking the bus to work, I sometimes set it to use both cores of my laptop's processor while in transit.  I only get roughly 30 minutes of battery life, but my commute is usually only 20 minutes, so it's fine.  I can generally get 3-4 hours, however, if I turn power saving mode on and don't use a lot of computing power.
 

Offline m.saffered

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Hey LeeE, as per your clauses like "If the laptop has a multi-core processor it may even shut down one or more of its cores" , than my question here is, if this phenomena occur than it mean we have the facilities of dual to tetra Cores but we can't use it.....?


Not on batteries.  Instead of getting perhaps two hours on a charge, with cores shut down and reduced CPU frequencies, you'd just get 15-20 minutes running time.  Check your specific model specs to find exactly what power saving strategies it uses and how long it's supposed to run for on batteries.  Then charge it up and see if you anywhere close to the claimed battery run-time while you're actually doing any useful work.

yeah.......i got it that..but the issues is that if cores in shutdown that obviously it's affect on ours CPU Frequencies , so may be at this point  desktop would be preferable...because just imagine that i have to purchase the dual core for special speedy purpose and this would happen than....
 

Offline LeeE

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I'm not sure I followed that, but by all means get a multicore laptop if you can afford the premium and plan to use it on a desk where you can plug it into the mains (and optionally use a larger monitor, with a proper keyboard and mouse too).  Power for power, a desktop will be cheaper but not as easy to move to different locations.  It depends on what you need to do.

I think JP's experiences are pretty typical (although I get the impression that 3-4 hours on batteries is a bit above average).
 

Offline Karen W.

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My little laptop..Note book (acer) runs for 1 hour 45 minutes pretty reliably... Then I need to turn it off to save information without damage..and plug her in to ac power.
 

nixietube

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I get about 7 hours on my Samsung NC10. The larger and much older Sony I have barely gives enough time to uncoil the AC adaptor before shutting down.
 

Offline Karen W.

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Wow Seven hours is great! Really quite incredible...is it a notebook or regular laptop?

Does it have a huge battery?

Thats poor time on the old Sony!
 

Offline Karen W.

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Here I just looked up the SamsungNc10:

"Samsung NC10-13GB 10.1-Inch Blue Netbook - Up to 6 Hours of Battery Life"

So where is the difference in yours.. you get an extra hour.. is your model slightly different?
 

Offline LeeE

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I get about 7 hours on my Samsung NC10. The larger and much older Sony I have barely gives enough time to uncoil the AC adaptor before shutting down.

Sounds like you've got the 6 cell battery option, as opposed to the 3 cell battery.  The Sony's battery is probably cream crackered i.e. it's been through too many charging cycles and needs replacing.
 

nixietube

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Here I just looked up the SamsungNc10:

"Samsung NC10-13GB 10.1-Inch Blue Netbook - Up to 6 Hours of Battery Life"

So where is the difference in yours.. you get an extra hour.. is your model slightly different?

I can find plenty of Google references to higher battery life.

I have had it for a year or so, soon after it came out. I only bought it because I needed an ultra light machine for travel. It is a standard model, apart from a memory upgrade ( essential in my opinion ). Removing the battery it says standard battery at 5200 mAh. I suspect higher capacities are now available.

There is nothing special about the machine as far as I can tell or in anything I have done, apart from turning off the bluetooth* and enabling max battery mode. I dont mind the drop in screen brightness when switching from AC power to battery. I dont thrash the hard drive constantly or max out the cpu.


* I have to manually hibernate, it throws an error if I just close the lid while it is running. ( it wants to go to standby )

I cant really fault this machine. It is perfect for my needs. The wireless works very well and the camera is excellent for video conferencing and presentations (hooked up to a projector). Long gone are the days of wishing I had access to additional data to answer questions .I also use it to download TV programs I have missed and hook it up to the tv directly ( computer monitor input on the back of the telly ).

 

Offline LeeE

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Funnily enough, both the three cell and the six cell batteries are described as 'standard' on the Samsung website.
 

nixietube

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oops.. I hit delete when I meant to hit modify.

repost:

I get about 7 hours on my Samsung NC10. The larger and much older Sony I have barely gives enough time to uncoil the AC adaptor before shutting down.

Sounds like you've got the 6 cell battery option, as opposed to the 3 cell battery.  The Sony's battery is probably cream crackered i.e. it's been through too many charging cycles and needs replacing.

Model: NP-NC10

"Even though it is one of the world’s lightest netbook in its 10.2" class, weighing just 1.33kg with the powerful 6 Cell battery option, the NC10’s innovative design is packed with the latest technology for maximum mobility and productivity. It also incorporates a range of practical features, like a normal-size, ergonomic notebook PC style keyboard, to simplify life on the move."

"Delivers longer battery powered performance of up to up to 7 hours* using the 6 cell option, independent of any power supply, for maximum freedom and mobility. This vastly improved battery life is guaranteed by the LED display and optimised processing performance of the Intel® Atom™ processor coupled with SAMSUNG’s class leading engineering. So you’re always ready to go anywhere and do anything.
* Based on Battery Mark Score."


I havent sat there with a stop watch! So forgive me if I am not accurate to the minute.. the point being it lasts a long time :)
 

Offline LeeE

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Heh - the pair of non-rechargable AA batteries in my old Psion 3a tended to last a couple of months with average use.
 

nixietube

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Heh - the pair of non-rechargable AA batteries in my old Psion 3a tended to last a couple of months with average use.

OMG I have one! .. what was that strange languge?.. OPL or something... I managed to write a couple simple programs... and I even had the fax modem thingy.. ( it never worked very well ).
 

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