Laptops - use whilst plugged in to mains or not?

  Neet 00:52 04 Feb 2004

I have just bought a new laptop (Dell Inspiron 5150) and have been told by a couple of people that I should not have it plugged into the mains all the time when I am working on it as this shortens the life of the battery. My understanding is that I should allow the battery to run right down before re-charging it, and not to continue working on the laptop whilst it is recharging. This of course is not always practical and convenient, and it is frustrating to have to stop what I am doing to wait for the battery to fully re-charge. I would appreciate any comments as to whether working on the laptop whilst it is connected to the mains really does dramatically reduce the life of the battery. What do you experienced laptop users do? The Users Manual doesn't seem to deal with this question at all.

  Giggle n' Bits 01:06 04 Feb 2004

not run from the mains as your people say. Batteries haver cells in them and if they are overcharged they do die off.

Laptops/notebooks are desinged and mainly run independant from the mains power. if your going to run it from the mains you might as well run a desktop/tower pc unles your moving from A - B daily.

  Djohn 01:34 04 Feb 2004

As Valco says and I've just had a look at a few sites for information on this. They all recommend that you use the laptop until the battery is low, then plug into mains power. You can though use the laptop while it is charging without adverse affect.

The general guide seems to be that most batteries will be good for 1000 charges. But each time you connect to the mains it will count as 1 charge, even if the battery is 98% charged to start with.

If working from home, then remove the battery and run from the mains only, unless of course you wish to charge the battery at the same time. This is not from personal knowledge, but from reading the many advice sites on best use of laptop and battery. j.

As Djohn says, remove the battery and run the laptop on mains power alone, replacing the battery should you need to recharge it.

I have been doing this for the last 18 months with no adverse effects! (yet).

  Sir Radfordin 08:35 04 Feb 2004

Surely the effect can't be that great since it would defeat the idea of having a docking station that charges the battery as you go.

There are some makes of laptop that refuse to turn on if the battery (even if dead) isn't installed.

The lenght of time the battery will last (during a single session) may well increase the older it gets but this isn't always to do with how it has been charged.

  stlucia 08:45 04 Feb 2004

What the contributors have said above is right -- rechargable NiCad or NiMh batteries or whatever the current equivalent is all last longer if discharged down to a certain level before being recharged.

Docking stations presumably have sophisticated monitoring and charging systems which will cause the least harm to the batteries by not charging them if they don't need charging ... or are they configured so that the manufacturers will sell more battery packs at £80 a piece (or whatever)?! As a matter of interest, does anyone have experience of battery problems with a docking station.

  Stuartli 08:59 04 Feb 2004

I wasn't aware that batteries had the ability to count...:-)

NiCad batteries should be completely discharged every so often, after around 10 recharges; Ni-MH batteries don't suffer from "memory" and can be recharged from any state. Even so, completely discharging every so often pays dividends.

I realise this is not strictly to do with laptop batteries, but if anyone wants a well made and very efficient "intelligent" AA/AAA fast charger then the Fameart PC05 I got from click here in Preston (a member of the Farnell Group) will fit the bill admirably.

It comes with both mains and car adapters, microprocessor controlled -dV detection, is timer protected to prevent overcharging, reverse polarity protection, bad battery detection and has an LED information display.

Price: an amazing £11.75 including VAT...:-)

  Neet 09:48 04 Feb 2004

Thanks everyone, I was getting very confused with all this talk about NiCad or NiMh batteries, so I checked the manual again and it says that the computer uses a Lithium-ion battery and a reserve battery. The Lithium-ion being the removable one. Does that make any difference to your comments?

  skeletal 10:21 04 Feb 2004

Like everything in life, charging batteries is a very complex subject! The technology they use does effect how and when you should charge them. Just think about you car battery; how many people remove it from the car once a week for a good discharge then recharge?!

NiCads are known for their "memory effect" where, if they are half discharged, then recharged, they think their capacity is only half of what it should be.

NiMhs, it is claimed, have no such effect and thus can be recharged from any state.

Li-ion should be as good/better than NiMhs, I believe.

The one thing that is pretty universal though, is never leave them discharged.

So, what I do with NiCads is completely discharge them, then recharge. All others, charge whenever/whatever the condition; then occasionally do a full discharge; then recharge.

The car battery would probably benefit from this, but it's too much hassle!!

Finally, you may not consider it's worth the worry of if/when/how you should use's meant to be used after all. The speed of things advancing in the computer world will mean your laptop is obsolete before the batteries have discharged for the first time!!!


  stlucia 10:59 04 Feb 2004

My experience of rechargeable cells is mainly in the model aircraft field, and I agree that NiMh and Lithium Ion are better than NiCad from the point of view of memory effect. But, the perceived wisdom is that it is also bad for the cells to COMPLETELY discharge them as well -- battery discharge/charge equipment (cyclers) will discharge them only down to a certain level beyond which they may not recover. I believe the level is 0.7 volts per cell.

Laptops are presumably designed to die when the battery reaches this predetermined voltage. Don't try to discharge them even further unless you've got a cycler that is programmed for the specific type of cells.

  Neet 11:36 04 Feb 2004

Thanks everyone. Djohn / Smiffy99 think I will do as you suggest, make sure it is fully charged then remove for when I am not on the move. Skeletal thanks for definitions and particularly for your sensible "lets not get our knickers in a twist" approach - that was exactly what I thought when I turned down the 3 year extended warranty!

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