Can I keep my MacBook pro plugged in all times while working on it?

When plugged in, the battery will charge until the smart charging circuitry and firmware say it is fully charged. At that point, charging stops. In order to keep the charging circuits from constantly cutting on and off as the battery slowly looses charge (all batteries loose charge, even when just sitting unused, they just do so very slowly), the system will not start charging again until the battery has depeleted by a fair bit (for most devices this will be somewhere between 4%-10% of the full charge). So, left plugged in, with a battery in good shape, your MBP will not begin charging again until the battery is say, somewhere down to 90%-95% of a full charge, which if just sitting idle would take at least a day or even two or three (depending on how old the battery is, and how much use it has had).

So no, you cannot overcharge it, no worries there.

P.S. my current MBP is a late 2008 model bought in 03/2009 - the battery has somewhere between 350-400 cycles on it (haven't actually checked it in awhile). It has spent probably 75+% of the time plugged in and other than when I'm away on vacation or something, it has been on 24/7 for the past 3 years (sleep timeout is 3hours, or I just close the lid when not using it). It does typically get unplugged and used in my lap for 20-30 minutes or more probably at least 2 or 3 times a week. Currently, I can comfortably work on battery power alone for up to nearly 3hours (using mail, safari, excel and likely word or a text editor, for example). So for a battery already well past 300 full cycles, it is doing just fine IMO. Oh, and I have probably calibrated the battery meter (ie. deep cycled it) only 6 times or so in those 3 years.

I know it's okay to charge Macbook all the time. The question is about the charger itself. Would the life of the charger be shortened by leaving it plugged in an A/C outlet 7 days a week 365 days a year ? Can you give a yes or no answer?

Hi Michael,

Very interesting answer and very well informing, thank you for it. I just purchased a macbook pro made mid 2012 and was looking for the same question and came across your answer. What I wonder now is how do you measure the battery cycles of your mac, I need to know that. Also, what is the approx life time of the battery if you have an idea since you are an old mac user?

Thank you so much for the information.

I bought a new Macbook Pro 2017 model 13 inch without touch bar a month ago.

I installed the coconout battery and I noticed some changes using it this month.

On my fist use, it said 2 battery cycles with full charge capacity 4883 mAh and design capacity 4790 mAh.

After few weeks, the battery reach 8 cycles and full charge capacity drops to 4634 mAh.

I ran it on battery until 5% once when cycles was 6.

Now I would like to know if can I get it up to 4790 mAh full charge capacity or did I damaged my battery?

Sure. Just exercise the battery once in a while. Letting it run down once every month or two will maximize its life.

Read: Apple - Batteries - Notebooks

Sure, many current and previous MBP owners do it all the time.

The thing is to not go weeks or longer without ever using the battery. So just try to unplug it a couple or few times a week, at least for a short while so it gets some regular periods of partial discharging and charging.

The battery will last best if you use it, at least a bit, regularly (every couple or few days say, but at the very least once a week). Also, avoid really deep discharges - partial cycles take far less of a toll on it than frequent deep cycles (such as running it down to the point it auto-hibernates on you), and frequently plugging and unplugging it will do no harm (no need to fully charge it either, every time you plug it in - "partial" cycles refers to partial discharges as well as partial charges).

Really, the only single reason to ever run it all the way down to auto-hibernation is to calibrate the battery meter, and as such, that really only needs doing very infrequently (I know Apple says monthly, but they err on the side of caution to make sure people do use their battery, I'm speaking from my own personal experience over the last 12 years of owning Apple laptops).

The battery does not overcharge, even if left plugged in at all times.

Check John Galt's link posted above:

Read: Apple - Batteries - Notebooks

According to this you can't.
http://superuser.com/questions/427099/why-is-keeping-my-mac-battery-40-80-charge d-advantageous