February 4th, 2008
MacBook Air Diary-Day 5: Battery observations
Apple quotes the MacBook Air as having a 5 hour battery, but as with most OEM statements about battery life, it should be taken with a grain of salt. The battery life figures quoted by most manufacturers are measured under perfect, almost never practical, circumstances.
They usually use a brand new battery, turn off all wireless (WiFi, bluetooth), no external peripherals connected (monitor, USB), they have the Energy Saver preferences ratcheted all the way down, keyboard backlights off and the monitor brightness set to one bar (the lowest setting.)
The MacBook Air ships with a sealed 37-watt-hour lithium-polymer battery and charges via a 45W MagSafe power adapter with a new right angle connector. According to Christopher Sinai’s excellent coconutBattery 2.5.1 the MBA battery has an original battery capacity of 5200 mAh.
I did some informal battery tests on the MacBook Air over the weekend and came up with the following results:
Test 1 - Intense use
In this test I set the MBA Energy Saver settings to never sleep the hard drive, and to never sleep the display because I wanted to use the machine the entire time. Display brightness was 12 out of 16 bars (about where I like it), WiFi and Bluetooth were turned on (although I wasn’t connected to any BT peripherals), playing a music stream from iTunes radio and installing software over Remote Disc (read: lots of WiFi and disk access). I also rebooted the MacBook Air once.
- First battery low warning: 3 hours, 26 minutes
- Forced sleep: 3 hours, 39 minutes
It’s not the 5 hours that Apple promises, but not bad given the admittedly intense usage pattern. I think that it should be pretty easy to get 4 hours of battery life out of and MBA with a modicum of conservation.
My MacBook Pro–2.4GHz Santa Rosa–running the exact same test got only 2 hours, 45 minutes of battery life, which the MBA bested by almost a full hour.
Charge time for a completely dead MacBook Air battery was 4 hours and 30 minutes while the machine was in use. You can expect it to charge a little faster if the machine is sleeping and a little faster still if it’s completely shut down.
One annoyance with the battery (after the fact that it’s non-removable) is that there’s no battery indicator on the bottom of the case as with previous MacBooks and PowerBooks. This is a really handy feature for travelers because you can quickly flip over the machine, touch the button and quickly see if you have enough charge to make it where you’re going. The MacBook Air forces you to open the lid and read the battery icon in the menu bar, which can be a hassle if you’re in a hurry and the MBA isn’t logged in–or worse, shut down.
