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18 hours on my mid-2013 Macbook Air battery!
- Thread starter Middleman-77
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GGJstudios
macrumors Westmere
The time remaining is a constantly-changing estimate, based on the current workload and settings on your Mac. As alphaod indicated, only a measurement of actual run time with normal workload until shutdown is indicative of true battery life.
GGJstudios
macrumors Westmere
No, Apple is not cheating you. Apple's estimates of time you can get on a charge are clearly stated to be based on specific conditions, which may or may not be the same conditions present on any user's Mac. They also say "up to 12 hours", so it is ridiculous to claim Apple is cheating anyone if they don't get 18 hours. The displayed time indicates the time remaining if the current settings and workload continued remained the same until the battery drained. It's no different than your car's estimate of distance remaining on a tank of gas. If you're driving 40 mph, you'll get one estimate of the distance remaining, assuming you maintained that speed. You would get a different estimate if you were driving 100 mph. Because your speed is constantly changing, the actual distance remaining on a tank is impossible to accurately estimate. So it is with battery life from a charge.
Drew017
macrumors 65816
Mine frequently shows 18+ hours when the computer is doing very simple processes, like when I'm typing a document with wifi off, brightness down etc. It's all relative to what the computer is doing. On ML I used to get an estimate of 20 hours, but Mavericks seems to be able to more accurately represent the time remaining. OP, in my opinion, being as the mid- 2013 MBA has such awesome battery life, don't worry about the time remaining 😛
The algorithm used takes into account CPU cycles, screen brightness, inputs, and power draw on external ports, as well as a few other factors. As these change, it recalculates and gives you another time.
If you put your screen as dim as it can go and still see the time, you can get almost a day out of it on a core 2 duo running Leopard. It's not until you raise it back up and start using it that it drops to 4 hours or so.
The best way to tell is to prepare to use it for an entire day. Give it a full charge and wait 2 hours to condition the battery. Then remove the charger, power it up, and start your clock. Once booted, record the estimated time.
Then as your laptop is about to shut off, compare the stop watch to the estimated time you wrote.
If you put your screen as dim as it can go and still see the time, you can get almost a day out of it on a core 2 duo running Leopard. It's not until you raise it back up and start using it that it drops to 4 hours or so.
The best way to tell is to prepare to use it for an entire day. Give it a full charge and wait 2 hours to condition the battery. Then remove the charger, power it up, and start your clock. Once booted, record the estimated time.
Then as your laptop is about to shut off, compare the stop watch to the estimated time you wrote.
polee
macrumors 6502a
GGJstudios
macrumors Westmere
You don't need to "condition" or calibrate the batteries in current Apple notebooks. Run on battery whenever you need to and plug it in whenever you can. You can plug or unplug any time you need to, regardless of the charged percentage, and you never need to completely drain your battery. Just make sure you don't run on AC power exclusively, as your battery needs to be used regularly to stay healthy.
The link below should answer most, if not all, of your battery/charging questions. If you haven't already done so, I highly recommend you take the time to read it.