Will Battery life be reduced if plugged in on 100% Battery?

As the title asks, I have heard in some places that if you continue to keep the laptop plugged in on a fully charged battery, it will eventually lower the battery life? I seemed to have noticed this on my old Dell, does anyone have experience or reliable information about this? Thanks

 

In theory, a well designed laptop should stop charging your battery when it reaches 99-100%, and then fully take power from the AC adapter directly. This should keep the battery from getting unnecessarily hot/worn out and live longer.

Personally, I've never seen the point. All batteries will die eventually, be it in 300 cycles or 280 cycles (or less in a faulty battery; Apple replaced mine twice because it lost significant capacity in less than 80 cycles, but they were just ty batteries that were recalled. Dumb Sony batteries...). If I take the battery out (not really easy on an M14x) when i'm using it on AC, and somehow my AC adapter gets unplugged, there goes all my work. No thanks, the battery is there for a reason.

Now, on the point of the M14x with its not easily serviceable battery, if your options are using it plugged in vs. running it on battery all the time, then I'd leave it plugged in at 100%. All batteries have a limit to the number of charge cycles they can go through, it's just the chemistry of it. The "degradation" to battery life by leaving it plugged in has got to be quite minimal compared to the wear caused by constantly cycling the battery (which is a reasonably finite number).