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Laptop switches between ac and battery


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8 replies to this topic

#1 dwong4555

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Posted 02 July 2012 - 12:40 AM

Dear Tech wizard, First of all I have a Hp HDX 16t premium laptop which i bought in 2009. I have had no major problems with it until now. My laptop has recently had the problem of switching between ac and battery when the ac power is plugged in. It happened all of a sudden. It was gradual at first but then it started switching more frequently. I tried diagnosing the problem and I have about exhausted all my options. I will provide a list below and what I believe is not the problem. 1. My HP does get rather hot so I tried to see if the heat caused a short or increased resistance in the circuitry of the motherboard. I always have a laptop cooling fan underneath but I added an extra desk fan to blow on the laptop to cool it some more. But the laptop still kept switching. So then I further chilled it by placing ice packs underneath the laptop. Still didn't work 2. I have tried removing all of the usb and periphery to see if it caused a short but no. 3. I have tried opening the laptop and looking at the circuitry to see if there were any burned parts but there were no obvious parts that looked like it was damaged or malfunctioning. 4. I bought a new ac power cable but that did not fix it. 5. The HP website told me that it could be a problem of the OS so i reinstalled the whole system to factory default. but that still did not fix it. so not a software issue 6. i have tried taking the battery out to see if the battery caused a short but the laptop cuts off when it tries to switch to the nonexistant battery What i have noticed: I have noticed that when I am using a processor intensive program such as a game or streaming multiple websites that it is when the switching starts. I have tried inserting a new battery and the power source remains on ac power longer but still switches but more slowly. When i do play intensive games the whole laptop will eventually completely shut off even if the battery is at around 40% charge while it is doing the switching What i haven't tried or think may be a source I have not tried updating the bios and i am thinking it could be a problem with the bios not recognizing the ac power well. The laptop is not drawing enough power. But the problem here is that the power cord came with the laptop and it has not malfunctioned up till this time. there is a short somewhere on the mother board which could be incorporating the above surmised sources. The short causes the bios to switch to battery because it is not drawing enough power from the ac cord. Would these problems be hard to fix by myself or would i have to send it in to be repaired? I have a degree in engineering and have worked plenty with sodering. I have even tried looking up chipmaps of the HDX but I dont even know where to start looking for the source of the problem. Thanks David

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#2 Doug

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Posted 02 July 2012 - 08:11 PM

Hi dwong4555 (David),

Though you seem to be a resourceful person and have tried some interesting avenues of investigation, we will probably need additional information to be of much help to you.

Since you have raised the issue of Heat possibly being the culprit here, could we get some data on Temperatures?
Have a look at this Post by our own excellent Digerati, regarding utilities which will help you monitor Temperatures.

Take particular note of temperatures around the time that the problem happens.

Now if it were me having that particular problem, I would be concerned that the A/C connector socket where the power source plug is inserted might perhaps have been damaged or stressed physically.
Physical damage to the A/C socket can bend the actual connection contacts, or can cause a micro-fracture of the MotherBoard where power is connected from source.

As an engineer, I am sure that you are familiar that with extended or heavy use, heat can rise. And when heat increases, it is possible that parts will expand, including any cracks that may have been caused by physical damage.

Another thing that I'd have a look at, would be the Power Settings under Personalize - Screen Saver - Power Schemes.
Let us know what the current settings are, and what options your machine allows.

And not least, it is important for you to inspect your Fan/air intake and exhaust.
If there is any accumulation of lint, dust, or debris, heat can build up to troubling levels.

Maybe this will get you started on some additional investigation.
And hopefully other knowledgeable Techs will contribute their thoughts.

Doug

#3 dwong4555

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Posted 04 July 2012 - 11:39 PM

Dear Tech Wizard, Thanks for all your help. Sorry that I am late in replying but i downloaded core temp and have been trying to compile data on when the pc starts to switch between ac and batt power. And as of right now I am sad to say i have not been able to get much conclusive data. I can tell you that my pc has been doing better however and has not been switching as much but when it does switch the battery does use less power so it drains much slower even when using demanding applications. but so far, my pc has been stable at aroud 50 degrees C for both cores. I have a intel core 2 duo p8700. But i noticed that when the pc goes about 60 degrees it starts to switch. A funny thing is that the first day that i installed it i noticed that whenever the second core starts loading more than the first core is when the laptop would switch to battery but when the first core loads more than the second core it would switch to ac power. But in the past few days it has not happened. it has been rather random now when the laptop switches and the loading for the cores have been random and no set pattern. Man i hate it when diagnosis does not have an easy pattern to figure out. :( i will continue to monitor the core temp and will post more data when i have any Sincerely, David

#4 terry1966

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Posted 05 July 2012 - 03:20 AM

4. I bought a new ac power cable but that did not fix it.


did this ac power cable come with the ac to dc adaptor? because to me it sounds like when the laptop needs to draw x amount of power (when both cores start being used above a certain %age) the adaptor isn't able to provide it and that's why it switches to the laptop battery or if not connected just switches off.

do you have another adaptor available to test with?

:popcorn:

Edited by terry1966, 05 July 2012 - 03:31 AM.


#5 Tomk

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Posted 05 July 2012 - 11:22 AM

Terry has expressed my thought also. I had a laptop reacting similarly. It turned out that a puppy had chewed on the cord from the power supply to the laptop. Only indication was very tiny teeth marks that were very hard to see... however, enough damage was done that the laptop starting operating as you have described. Truthfully, I still use the power supply but I know where to "wiggle" the wire when things foul up. (I did purchase a replacement power supply but hate to use it as long as I can get the old one to work.)

#6 dwong4555

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Posted 06 July 2012 - 09:16 AM

Ah yes the new power supply I bought was an official HP power supply 90W from best buy. Basically the same one that came with my computer when it was new. Even the old one did not have any frays. i basically use it as a desktop since the battery life is so bad. But recnetly my laptop has been doing much better. it has been switching less so almost enough to keep the battery charged steady so it is not draining as much. the only thing that i did was jiggle and electrically insulate a few wires near the power socket. could it be that the other wires touching the power wires were causing interference? i also updated my drivers on the WAN adaptor.

#7 terry1966

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Posted 06 July 2012 - 11:09 AM

i wouldn't have thought the wires or update would affect anything, and seeing how it's a complete new power adaptor lead, i'd start suspecting the port where you plug the power into the laptop, it's probably worn or dirty and not making a great connection with the power plug, so any slight movement of the lead causes it to break and lose power, that's when it switches to the battery. :popcorn:

#8 Doug

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Posted 06 July 2012 - 12:01 PM

i wouldn't have thought the wires or update would affect anything, and seeing how it's a complete new power adaptor lead,
i'd start suspecting the port where you plug the power into the laptop, it's probably worn or dirty and not making a great connection with the power plug, so any slight movement of the lead causes it to break and lose power, that's when it switches to the battery.

:popcorn:


Through process of elimination you have possibly come back to inspecting the plug and socket where the power cord connects.
Didn't I already mention that?

Now if it were me having that particular problem, I would be concerned that the A/C connector socket where the power source plug is inserted might perhaps have been damaged or stressed physically.
Physical damage to the A/C socket can bend the actual connection contacts, or can cause a micro-fracture of the MotherBoard where power is connected from source.

As an engineer, I am sure that you are familiar that with extended or heavy use, heat can rise. And when heat increases, it is possible that parts will expand, including any cracks that may have been caused by physical damage.


dwong4555

Though it is not an entirely reliable diagnostice and is also not a permanent solution... Have you noticed whether or not the problem occurs more often or coincident with slight movement of the machine or power supply cable.

Can you "cause" the problem to occur by gently giggling the power supply plug where it enters the machine?
Can you "correct of fix" the problem when it is occuring by either giggling lightly or applying gentle pressure in various directions, upon the power supply plug at the point where it enters the machine?

It the above does turn out to be true, you could have a damaged power connection socket, or the power connection socket may have micro-fractures where the solder connections transfer power to the motherboard.

#9 Lee

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Posted 10 July 2012 - 03:06 PM

First of all I have a Hp HDX 16t premium laptop which i bought in 2009


With regard to the heat issue. Considering the laptop is a few years old, it does sound like it is time for a dust clean-out rather than external fans and cold packs.

The fan outlet after three yrs. of use:
photo_4.JPG

I recently cleaned out the dust on a laptop of similar age and the temps dropped remarkably. Unless you are very confident and tech. "handy" ( How to take apart a HP laptop ), this is a job for an experienced laptop service center.

The power issue may or may not be connected to the heat problem.

PS.
If the laptop is being used as a desktop only as you say, the battery should not be in the laptop at all as its being constantly charged. If it's a Lithium battery, it should be stored at a 20-40% charged state in a cool dry place. The battery should be installed every couple of months to bring it up to full charge and used back down to 20-40% and put back in storage.
If it is a replacement battery (especially off ebay) I'd be very suspect about it's quality, as many are very old issue (but still new) that manufacturers get rid off cheap, or worse still, a cheap and poorly made copy.

Cheers,
Lee

Edited by Lee, 10 July 2012 - 03:41 PM.

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