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Paper Tape
Posts: 3
Registered: ‎02-16-2012
Location: Australia
Message 1 of 13 (4,938 Views)

T420 slow only if battery not plugged in

[ Edited ]

Hi there,

 

I recently bought a new Thinkpad T420 (specs see below) in Australia directly from Lenovo, and it seems to work flawlessly most of the time. Now the only weird thing I noticed is that everything is slow when the battery is not plugged in (but the power cord is). But first of all my system specifications:

 

Thinkpad T420

Intel Core i5 2520M, 2.50 GHz

Intel HD Graphics 3000

4 GB RAM, a 128 GB SSD, 6 cell Li-Ion battery

Windows 7 Professional 64 bit and Ubuntu 11.10 64 bit are installed

 

How I found out about my problem:

  • In January, when I just got the notebook, I installed Mirror's Edge on Steam and played it a bit. Everything worked fine and I had a high framerate on low details. Both the power cord and battery were plugged in.
  • I stopped playing any games for a few weeks, and someday I noticed a few things were slower than before, like extracting files, opening applications took longer, etc. I didn't think about it too much because it was still faster than with my previous notebook.
  • I wanted to continue Mirror's Edge, but the loading times were a lot longer and the framerate in-game a lot lower, and I never changed any settings. Other games, even those not requiring much performance (such as Bit.Trip Runner or Half-Life 1), seemed to run a lot worse as well. And that's how I started to investigate.
  • I noticed that at some point in January or February I had unplugged my battery and put it to the shelf, because I was using my notebook with the power cord almost all the time.

 

Here's what I found out so far:

  • It's independent of the operating system. Both Linux and Windows are slower when the battery is not plugged in, and run at normal speed when it is.
  • It seems to affect both graphics and CPU power, but I'm not 100% sure. Mirror's Edge is running at a much lower framerate without the battery plugged in, but extracting files, opening applications or doing other CPU-intensive things is slower.
  • Only the battery state makes a difference. I can keep the power cord unplugged or plugged in, the performance doesn't change. Only when the power cord is plugged in and the battery is not, things are slow.
  • The performance can be changed instantly by plugging in the battery or unplugging it. I can start Mirror's Edge for example, with the battery plugged in, and everything works normally. If I remove it, all of a sudden the framerate drops significantly. As soon as I put it back in, things are back to normal. The same works with different tasks and also on Linux.
  • Changing SpeedStep or Adaptive Thermal Management settings in the bios doesn't make a difference. I've tried most combinations (Maximum Performance, Battery optimized, for both AC and battery) and it's always the same.

 

There are no other bios settings I changed that could possibly have such an effect.

This cannot be a driver problem as I am up-to-date with all of my drivers on Windows, and I am using an up-to-date kernel on Linux. Besides, the fact that it happens on both operating systems rather confirms my theory. If it were a driver problem, either things would work correctly or they wouldn't - but the battery state wouldn't make a difference.

 

Now, my questions are:

  • Could there be any explanation for this behavior or is it just bad hardware design?
  • Did it happen to anyone else? Is it a common Thinkpad thing, is it just my model series, or just my specific device which is not functioning correctly?
  • Is there any way to fix this?

 

As I need my notebook, it is hardly an option to send it back and wait for it to be repaired or replaced. I am keeping the battery plugged in all the time for now, but usually when I don't need it, I let it discharge to 40-60% and then store it somewhere else, because that's better for lithium batteries. However, I can't do that now.

 

Any help would be appreciated. If you need more information, just let me know. Thanks.

Fanfold Paper
Posts: 16
Registered: ‎02-17-2012
Location: United States
Message 2 of 13 (4,911 Views)

Re: T420 slow only if battery not plugged in

[ Edited ]

I just got my T420 yesterday, and the situation is true indeed. The moment I take out my battery, CPU switches to 800MHz, which is the lowest frequency.

 

I searched quite a bit, tried:

1) Set all modes to "Maximum Performance" in BIOS

2) Set processor.ignore_ppc=1 in grub

3) Verified that I am using the latest BIOS

 

Some people point to the incapable 65W adapter. I did find when my machine is at full-load, the charging time approaches infinite (<1%/hour). However, if it's the default power adapter, it should be capable of running my machine, right? Or did Lenovo get dirty and try to force customers pay additional money for a power adapter after each purchase?!

 

This problems seem to exist for a long long time, with plenty of discussions. Why didn't Lenovo solve it? At least some official reply or FAQ page?!

Community SuperMod
Posts: 4,163
Registered: ‎04-25-2008
Location: US
Message 3 of 13 (4,903 Views)

Re: T420 slow only if battery not plugged in

Hi Guys, and welcome to the Lenovo User Community! This has been discussed at great length over the years. There are community knowledgebase articles. Start with this one: http://forums.lenovo.com/t5/Welcome-FAQs-Knowledge-Base/Should-I-run-with-my-battery-in-or-out/ta-p/...
I don't work for Lenovo. I'm a crazy volunteer!
Paper Tape
Posts: 3
Registered: ‎02-16-2012
Location: Australia
Message 4 of 13 (4,898 Views)

Re: T420 slow only if battery not plugged in

Hi,

 

thanks for the replies to both of you. I actually still have the 90W power adapter of my old R61 Thinkpad. I tried connecting it and in fact it did work at full speed with the battery removed.

 

However, I noticed some (very slight) crackling noises coming from the power adapter (like this high-pitched sound, interrupted every now and then), so I'm using the new 65W one again. The 90W one of my R61 actually should work fine, but on the other hand I don't feel too comfortable using it.

 

Shame on Lenovo for suddenly shipping high-quality Thinkpads with inferior 65W adapters, and not even informing customers about that issue.

Community SuperMod
Posts: 4,163
Registered: ‎04-25-2008
Location: US
Message 5 of 13 (4,893 Views)

Re: T420 slow only if battery not plugged in

[ Edited ]

Hi Himmelflugzeug!

 

I'm sorry that your laptop doesn't behave as you expect when you remove the battery. This has been a common design decision of laptop vendors for many years. There's nothing inferior about the 65W adapters - the systems run as specified, as long as critical parts are not removed. I'm a highly mobile user, and would complain if they shipped bulkier, heavier 90W adapters.

 

Don't forget that if AC power is disconnected with the battery removed, you may lose data or at worst suffer damage to the laptop.

I don't work for Lenovo. I'm a crazy volunteer!
Guru
Posts: 9,456
Registered: ‎12-26-2009
Location: CA
Message 6 of 13 (4,881 Views)

Re: T420 slow only if battery not plugged in

I think the CTO order page should allow buyers to choose an alternate adapter instead of the default one, rather than in addition to.
W520: 2960XM, Q2000M @ 1091/1380, 32GB RAM, 500GB&750GB HDD & 500GB SSD, FHD&MB168B+
X61T: L7500, 4GB RAM, 500GB HDD, XGA screen, Ultrabase
W550s: 5600U, K620M at 1164/1281, 16GB RAM, 512GB SSD, 3K touchscreen
X200s: SL9400, 6GB RAM, 64GB SD card, WXGA+ screen
TPT1: 1839-23U
Fanfold Paper
Posts: 16
Registered: ‎02-17-2012
Location: United States
Message 7 of 13 (4,870 Views)

Re: T420 slow only if battery not plugged in

[ Edited ]

My part of update: I submitted a support ticket yesterday, and got a callback this morning.  He asked me to run the diagnose tool on support page to check HW problems.  Haven't tried yet, but I guess there aren't any as this thread describes the only problem I am experiencing with (and it's common obviously)

 

I maybe one of the unfortunate person that do need to run hour-long jobs that heats up the entire laptop.  Therefore I really want to remove the battery if possible.

 

Can any T420 owner confirm that a 90W supply works?  I probably would just buy one as I really need full performance on AC only.

 

Update:  Tried the HW test and it's just standard RAM test and disk s.m.a.r.t test.  Absolutely useless. 

Bit Torrent
Posts: 2,413
Registered: ‎04-08-2011
Location: USA
Message 8 of 13 (4,852 Views)

Re: T420 slow only if battery not plugged in


wujj123456 wrote:

 

Can any T420 owner confirm that a 90W supply works?  I probably would just buy one as I really need full performance on AC only.


You can use the 90W or 135W ThinkPad AC adaptors with the T420.  I do daily.

Fanfold Paper
Posts: 16
Registered: ‎02-17-2012
Location: United States
Message 9 of 13 (4,848 Views)

Re: T420 slow only if battery not plugged in

[ Edited ]

Thanks for the info!  Where did you buy your adaptor?  The ones on Lenovo website seem to be several times more expensive than the ones on Amazon.  But I do want to stick with geniune ones. 

 

Edit: never mind.  The ones on Amazon are also posted by Lenovo, and should be fine.  I will just go with those ones.  I didn't see any 135W adapters, but I don't think I need that anyway. 

Bit Torrent
Posts: 2,413
Registered: ‎04-08-2011
Location: USA
Message 10 of 13 (4,836 Views)

Re: T420 slow only if battery not plugged in

I have quite a few ThinkPads so I use mostly 90W.  But because I have a W510, I also have a 135W adaptor at my desk in the "generic" spot.  The other 135W is plugged into the Series 3 dock.  Therefore, if I'm using a ThinkPad at my desk, they are always plugged into the 135.

 

At the couch and other locations it's the 90W.

 

 

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