[Nottingham] Laptop battery lifecycle

Graeme Fowler nottingham at mailman.lug.org.uk
Sat May 17 15:07:01 2003

On Sat, 2003-05-17 at 14:53, Martin Waryniak wrote:
> When you turn off your Laptop, is it best to leave it plugged in into 
> the socket or should you completely unplug the laptop from the socket 
> and let it stay on battery power?

As it's not using any power when turned off (providing it's not simply
"asleep") it makes no real difference, allowing for the fact that the
battery will naturally "drip" discharge over time anyway even when not
is use. I've always kept mine off mains when powered off, unless the
battery needs a charge.

> I am just wondering because I used to always leave my notebook
> connected 
> to the power socket when i wasn't using it but recently i stopped
> doing 
> that. I have a feeling that my battery lifetime has decreased but i am
> not sure because I hardly ever use the notebook on battery only.

...which could explain why the battery life is decreasing (apart from
the age of the battery, since they do "go off" over time). Most
rechargeable batteries - regardless of type, although the older NiCad
type exhibit this most - have a "memory". If you don't fully discharge
them, they can be difficult to fully charge after a time. The length of
time obviously depends on the battery type, the rating, the load and the
number of cycles it's been through.

It's good practice to completely drain laptop batteries (as near as is
possible) once in a while, and then fully charge them with the system
offline. Continually running on mains means the battery remains "topped
up" and never gets fully discharged - this is what can cause the memory
effect, meaning that the battery is incapable of taking a full charge.

I try to let mine run down close to flat - getting warnings that the
system is about to go to sleep - once a month or so. Works for me!

YMMV, DYOR, IMO etc :)

Graeme Fowler <graeme@graemef.net>