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In windows 7, the battery of my core i7 VAIO would always only charge until 79 % however, in ubuntu it charges 100 % i heard from a friend that it is dangerous for battery to become charged fully and stays that way while the charger is still plugged in. i always have my charger plugged in. so is there a danger to my battery? or is there a way to manage battery options?

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"i heard from a friend that it is dangerous for battery to become charged fully" demand proof from him ;) – Rinzwind Dec 27 '12 at 19:48
Sounds like your battery is already broken.... And why would it be dangerous for the battery health(I presume you mean that) to fully charge it? Tell your friend to get his facts straight. – Dr_Bunsen Dec 27 '12 at 19:51
I can confirm leaving it charged in may cause a Vaio to lose battery's capacity. It's such a problem that Lenovos even have a battery limiting feature to limit charge to 57% or so, to keep it from constantly topping off the battery charge when plugged in. – NoBugs Oct 3 '13 at 14:53

Laptop batteries have a micro controller which switches the power drain from the battery to OFF when plugged in to an adapter. Leaving the laptop plugged in will not harm the battery. However, batteries have a lifespan, and depending on the manufacturer can last you a year or more. Eventually, the battery will go bad no matter how much care you put into it.

According to the manufacturers they advise you to Unplug your charger once your battery is fully charged.Even though it shouldn’t make a difference if you don’t unplug it i advise you to unplug it once your laptop is fully charged!

You could also install a software/app which notifies you once your laptop is fully charged.look into this link for the software/app.

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Sometimes Windows laptops can develop a "battery memory" and gradually hold less and less of a charge. It is caused by not fully charging and draining a battery, and can be fixed by fully charging and draining the battery several times. However, I think that was limited to older machines, so it may not be your problem. Windows 7 on laptops can have trouble recognizing an old battery. On mine, it used to say I had a full charge, even though the battery no longer worked. Your battery may be having charging issues that are confusing Windows. How long does it last for? P.S. It's not dangerous to keep your laptop plugged in and the battery full, unless it overheats. Keep it on a cooling mat and you're fine.

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Memory-effect wih batteries was a thing to know with olders NiCad- and NiMH-batteries from 10 years ago. Today's batteries and especial today's LiIon-batteries shouldn't be fully charge and drained. This might even reduce the battery life-span. Wikipedia has an interesting article about memory-effect – MadMike Jan 24 '15 at 12:26

Two older types of batteries, once popular in portable computers, are nickel-cadmium (NiCad) and nickel-metal hydride (NiMH). A NiMH battery is longer lasting than a NiCad, but it too woefully suffers from The Dreaded Memory Effect.
It has to be discharged very often. For example, after you use, drain it til your computer shuts down and recharge it again to make you battery more healthy. That progress is really painful for lazy people like me.
Fortunately, with new Li-ion battery type, it wouldn't be a problem if you keep charging your battery even it's full. In my opinon, it would be better to drain your battery 2-3 times per week to ~30% and then recharge it.

Source: The different types of laptop batteries!

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There is an excellent post on how to make sure the battery only charges to 80%. It started out as a question about a Lenovo laptop, but it might hold for your case as well. It uses the tp_smapi kernel module.

I personally find this one of the best battery management strategies.

Here is a quote from the post by aquaherd:

install and load the tp_smapi kernel module:

sudo apt-get install tp-smapi-dkms
sudo modprobe tp_smapi

and write the desired charging thresholds to virtual files in /sys/devices/platform/smapi:

echo 40 | sudo tee /sys/devices/platform/smapi/BAT0/start_charge_thresh
echo 80 | sudo tee /sys/devices/platform/smapi/BAT0/stop_charge_thresh

Good luck.

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No. tp_smapi is ThinkPad-specific. Good suggestion if it was about a Thinkpad, though. – gertvdijk Dec 27 '12 at 23:31
Can you suggest an alternative for VAIO? – don.joey Dec 28 '12 at 8:44
No, most vendors don't have this available. I only know of Lenovo ThinkPads to have this feature of controlling the embedded power controller. – gertvdijk Dec 28 '12 at 12:13

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