Feb 13, 2007

When do I unplug my laptop?


What is the right way to treat my notebook regarding recharging. It mostly lives on my desk and acts as a desktop; I take it elsewhere in the house or yard once every day or two, for maybe an hour. For the rest, it's at my desk. So the question is: can I leave it plugged in and sleeping?


So, here's the protocol:


If the laptop is fully charged — it has a green light on the Apple adapter, or it says "100% Charged" in the battery menu — AND you're done using it, close the lid and unplug it.


If it's not completely charged when you're done working, close it to put it to sleep and let it charge all the way up to green, and THEN unplug it.


The longer the laptop is plugged in while the battery is fully charged, the more stale the battery will get, and the shorter its life.


Lastly, every couple of months, one will want to run the battery down to absolute zero — the screen goes black and won't wake up, but the light on the front still glows — then plug it in and charge it all the way up in one go. This conditions the battery, sort of reminding it how much capacity it should have. One should do this to a brand new battery also, AFTER charging it all the way up the first time.


By way of example, my current PowerBook battery, now 2.5 years old, has a fine 2-to-3-hour lifespan, because I have it unplugged so much of the time.

2 comments:

Joe6paq said...

Nice post, but I think it might be a little misleading. Particularly this: "The longer the laptop is plugged in while the battery is fully charged, the more stale the battery will get, and the shorter its life."

OS X won't "top off" a fully charged battery (charged 95% of capacity and above). So leaving your laptop plugged in all day while you are using it is your best bet.

Battery cycles (1 cycle = 1 full charge + 1 full discharge) are a bigger concern for battery longevity.

Curious about the state of your battery? Open Apple System Profiler and click on "power". It will show you the full capacity, current charge state and number of cycles that your battery has seen.

Jonathan said...

Very cool. I never noticed battery stuff in System Profiler. And I totally agree with "laptop plugged in all day while you are using it," but it seems clear from what I've experienced that leaving laptops plugged in during the many hours of inactivity cuts heavily into battery capacity and longevity. It's amazing, but so many laptops stay plugged in nearly 24/7, and after two years of that, a battery might squeeze less than an hour out of a full charge.