simple question about battery use

I have been told by friends that on a laptop once the battery is fully charged, one ought to run the laptop on battery till it discharges.I tend to leave the laptop on mains ( even when battery is fully charged), till I have to move the laptop to a different place/ room. Any views on this please!!

You have been misinformed. Modern batteries are not at all keen on being fully discharged, and this can significantly affect their working life. (They're not too keen on being overcharged either.) The best practice is to keep them topped up, don't let them discharge fully, but don't keep them on charge once fully charged.

I tend to leave mine on mains most of the time but use it on batteries once a week for an hour or so, just so that I know the batteries still work!

The main killer for modern laptop batteries is heat.

If you normally use it on the mains, unless you need the battery to handle a power cut it's often recommended to take it out. Ideally put it in the fridge, but that may be a bit OTT

Edited by billford (Mon 20-Jun-11 12:38:13)

In reply to a post by AEP:

You have been misinformed. Modern batteries are not at all keen on being fully discharged, and this can significantly affect their working life. (They're not too keen on being overcharged either.) The best practice is to keep them topped up, don't let them discharge fully, but don't keep them on charge once fully charged.

No quarrel with that, except to say that the control circuitry in the battery pack should prevent over-charge.

One point, more or less on topic, is that if the batteries don't occasionally go into deep discharge the "how long left" calculations get a bit fictional.

For Apple laptops, if the accuracy of that calculation is important they suggest it's "re-calibrated" occasionally (every few months) by running the battery completely flat (ie use it until the computer goes into hibernate mode, then leave it for a few more hours) before re-charging.

I'd imagine the same applies to PC laptops, they're much the same batteries.

My Samsung Netbook has a Battery Life Extender" option which, when set, only charges the battery to 80% when left on mains.

So, leaving the battery on charge, when fully charged does not seem to be a good idea.