Is it sensible to leave a laptop constantly on charge?

  Sandyums 21:42 26 Oct 2012

I have a new Samsung ultrabook and it sits on my desk for 3/4 of the day. The battery life is currently great and I want it to stay this way if possible. I know there used to be a problem with over-charging laptop batteries if you left them plugged in for too long but I want to know whether this is still a problem any more. The laptop doesn't have a battery which is easily removed so I haven't got the option of taking the battery out when connected to mains power.

In short, would it be better for the battery if I were to leave it plugged in constantly or would it be better to unplug it when it reaches 100% charge, let it run down and then plug it in again when it's almost empty?

  woodchip 21:46 26 Oct 2012

NO, Nothing wrong with it connected to the Mains when using it

  Forum Editor 23:57 26 Oct 2012

This a subject on which no two people ever seem to agree. Your battery will not be overcharged by leaving the laptop running on mains power - the battery is protected against that.

Some people take the view that a laptop battery has a working life of around three years in average use, and that isn't materially affected, whether mains power is permanently used or not.

Others say that's not true - a battery's life will be shortened if it's permanently fully charged.

What I can say is that I have had quite a few laptops, they have been heavily used, and are mainly (but not exclusively) used with mains power connected. I have never felt that the life of a battery has been shortened by doing this, but then how would I know? I've never done any proper tests.

What I have never done is remove the battery whilst working on mains power.

  mooly 08:47 27 Oct 2012

As above...

Li-ion battery technology doesn't support so called trickle charging (to do so would destroy the battery very quickly) and so all (to the best of my knowledge) laptops simply charge to 100% and then stop the charge process. The battery then begins to naturally self discharge at a slow rate (anything between say 0.2 and 1% per day). When the charge reaches around 96% the charge cycle is started again and the battery brought back to 100%

So leaving plugged in is no detriment. Removing the battery absolutley defeats the whole point of a laptop, removes the safegaurd of it having an uninterruptible supply and still dosen't stop aging of the battery which happens from day 1.

To go further than this, and I personally believe on what are normally mains powered systems that it is good to use the battery occasionally (say once every three weeks or so). A very occasional discharge almost "down to the wire" also seems to do no real harm. I have a 6yr old Acer laptop that has followed this regime and I would say the battery is still as good as I remember it when new on the odd occasions where I need battery power.

  morddwyd 10:26 27 Oct 2012


Thank you for that, particularly the first paragraph.

Like you, I have an Acer, normally connected. Sometimes the power lead comes out (like at the moment), and when it does I just leave it to run down, either to the warning message, or occasionally to shut down.

  Forum Editor 11:17 27 Oct 2012


You should never leave a laptop running on battery until the battery is completely discharged - that will stress the battery, and can even damage it.

If you're going to use the machine on battery power you should perform partial discharges to capacity levels of around 30%, and perform frequent charges, instead of performing a full discharging followed by a full charging. That way your battery will be healthier, and will last longer.

The other thing to watch, if you're working on mains power, is that the battery doesn't get hot - heat is the enemy of laptop batteries, especially when fully charged. In general terms the battery is likely to heat when the machine is getting intensive use - mainly when gaming - and the processors are working flat out. If you feel your machine getting hot when on mains power, take the battery out for a while.

  morddwyd 20:15 27 Oct 2012


Thank you

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