I want to use my monitor and prolong the battery!
July 28, 2011 10:29 AM   Subscribe

Will connecting an external monitor to a new Macbook Pro wreck the battery life?

I currently have an old (mid-2007) Macbook Pro which I plan to upgrade to the new 15" model sometime very soon. I am currently using an external monitor with my laptop in clamshell mode. Even though the monitor has it's own power plug, the laptop will not stay on in clamshell mode under battery power, so in order to preserve what little battery life I have left, I usually just take the battery out and run the laptop directly from the AC cord.

So the new MBPs have this (even more expensive) installed battery. I can't find any good information online about whether
a) the new laptops will run an external monitor in clamshell mode from battery power -or-
b) keeping the laptop plugged in all the time will wear out the battery faster.

I do sometimes take the laptop out and about and run it off of the battery, but it is my primary computer, so most of the time I use it at home, and the external monitor is better for me ergonomically (plus it's a bigger screen).

Despite having always religiously followed Apple's advice regarding battery usage and preservation, they never seem to last as long as Apple says (*shakes fist at Steve*). So before I plunk down $2000 on a new laptop, does anybody have any advice re: battery life in the new models and external monitors?
posted by DiscourseMarker to Computers & Internet (6 answers total)
Modern laptops are sufficiently smart about their power usage to avoid overcharging the battery even if you keep it plugged in all the time. Don't worry about it. The battery life isn't going to be as long as advertised--it never is--but it won't be because of this.
posted by valkyryn at 10:49 AM on July 28, 2011

To answer your first question, it will not run in clamshell mode on battery power. For whatever reason, that's just not something Apple will let you do. But as valkyryn said above, don't worry about leaving it plugged in. That's not really a problem with modern machines. If you worry about it anyway, just try to let it run all the way down every few weeks.
posted by duien at 10:52 AM on July 28, 2011

My wife's mid-2010 MBP is plugged in all the time and the built-in battery seems to have lost maybe 1 and 1/2 hrs of charge capacity over the last year. Nothing unreasonable, I think.

I've been operating my mid-2008 Macbook Pro with a second monitor (extended desktop) for 3 years. When I unplug, it says that it has 3 hrs of battery charge but IRL it works out to about 2. I always leave the battery in because I need a chance to save my work if there's a power interruption.

I've been very neglectful about letting the batteries run themselves down to recalibrate monthly.
posted by bonobothegreat at 11:33 AM on July 28, 2011

Your laptop is not an electric drill.

You can leave it plugged in as long as you want without damaging or running down the battery. You can charge it halfway, a quarter of the way, WHATEVER.

Budget for a new battery in 3-4 years if you're planning to keep the laptop longer, and seriously don't sweat it. If you're plunking down $2k on a new computer, it's not worth constantly stressing about following the battery charging superstition du jour over a part that costs $120 to replace, and will wear out in 3-4 years, regardless of how you use it.
posted by schmod at 12:58 PM on July 28, 2011

Just as a data point, I had a couple ~2006 MBP batteries die in under 2 years with maybe 10-15 cycles on them. I attribute it to leaving it plugged in 24/7 and only running on battery when I was on vacation a few times a year. Maybe it was the machine itself having a problem with the charging? Who knows.
posted by pjaust at 6:14 PM on July 28, 2011

Actually, you can get a Mac to run in clamshell mode on battery power. Google an app called InsomniaT, I've gotten my Macbook Air (13" mid-2011, Lion) to do just that.
posted by signalnine at 9:00 PM on July 28, 2011

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