I bought a Macbook Pro last week. I mostly use (and plan to use) it like a desktop with an external monitor. I use the system at least 15 hours a day. Now using the coconut battery application, I figured out that the capacity has the current capacity has reduced to 98% of the design capacity. I was wondering what is the best way to manage battery.

  1. Should it be always either charging or discharging
  2. Should it be plugged in all time.
  3. I barely get 2 hours and 30 minutes on battery. Is that normal? I run XCode, VMWare Fusion (for Visual Studio), Mail app, Chrome (5-10 tabs) and Itunes (mp3). The brightness is 60% on battery. I already did the calibration.

2 Answers 2


Xcode (especially 4.1) is a HUGE CPU hog. Same with VMWare Fusion. I think you're getting a fair amount of battery for the amount of usage.

It's fine to leave it plugged in, but try to do a 50% discharge once per month. The new MPBs have a built-in system that automatically discharges the battery about 1-5% and then re-charges them to keep the juice flowing. That's why you'll sometimes notice that the laptop is charging even if you haven't disconnected it.

Do not keep charging/discharging it, if you don't have to, as this increases the number of charge cycles. MBP batteries will have 80% charge capacity even up to 1000 charge cycles.

Your 2.5 hours is very good for the intensive work, especially considering that you run Xcode and VMWare Fusion, which runs windows, which runs an additional development suite. Don't forget, compiling code takes a HUGE amount of CPU. Chrome (and Flash) obviously take some. Mail and iTunes are least of your worries.

As a bonus, consider using http://codykrieger.com/gfxCardStatus which lets you monitor when the GPU is being used. GPU also takes up precious electrons.

  • Isn't the 2% capacity loss in 2 weeks a cause of worry. I would have done around 20 charging cycles. Sep 24, 2011 at 23:49
  • 2
    Coconut's calculations are incorrect. They're using the 1000 cycle count to mean that it'll be at 0% when 1k is up. (2%/20cycles * 100% = 1000 cycles.) Not true. Apple's specs say it's going to be 80%. I would look at System Information instead of 3rd party app. With that said, 1) make sure your coconutBattery is up to date, they had a bug (from website): "Fixed a bug where the "Design capacity" value was not correct on new MacBook Pro models". 2) If the charge capacity falls below where you think it should be, do a SMU and PRAM reset and SMC reset.
    – AWF4vk
    Sep 25, 2011 at 1:59

If you use your Macbook and you are working with it close to a power socket you should absolutely have it plugged it. Why make the battery go through more charging cycles when it doesnt have to or work on reduced power. Apple recommends that every so often you should let the battery run down completely and then fully recharge it (perhaps every couple of months).

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