Leaving power plugged in when fully charged?

I am trying to ensure I look after my battery as much as possible. If I don't need to use the battery (eg at my desk when I have access to power) should I leave the laptop plugged in or should I take it out once its 100% and let the battery discharge fully. Which method is better for the battery in the long term?

 

You'll probably get some differing answers on this, but here's my $.02.

Modern lithium batteries are designed with a certain number of charge/discharge cycles in mind, and their performance begins to degrade as the batteries age. Li-ion batteries will go bad setting on a shelf, even under perfect storage conditions having not seen a single day of use. They also don't display the "memory" effect that Ni-Cd batteries do, so you don't have to treat them with kid gloves like you would a cheaper battery type, always trying for a complete discharge, etc.
(Car makers using them in hybrid vehicles do keep the charge cycles tightly controlled because their interest is to get the maximum amount of time out of the battery pack as they can. After all, warranty replacement is expensive!)

The charging circuitry on the laptop's motherboard keeps tabs on the battery, and won't let the unit overcharge (fire!), or continue to feed it voltage. In fact, the next time you're charging the laptop and using it at the same time, take note that the plugpack will get cooler after the battery is finished charging, since it's no longer passing enough electricity to both charge the battery and run the machine itself.

 

I say just set a max charging threshold in Power Manager of 70-80 or 80-90%. Batteries tend to degrade faster if you leave them fully charged.

You don't always get full performance if your battery is not attached, and you run the risk of losing yor data if the power disconnects.

 

Ditto above.

 

On my X220, i've left it at the default setting of "automatically optimize for battery lifespan". When at home i always charge it to full and then run the notebook off the battery for 10-12 hours before charging it again and so on

 

It's been some years since notebooks tried to keep pushing charge into their batteries. Most, once the battery reaches 100%, won't top it up again until the charge drops a few percent. As already noted, Lenovo's Power Manager lets you define your own thresholds. However, if you make your lower limit quite low then you could get caught out if you do need to use the battery.

John