Will leaving my MacBook charger plugged in into my MacBook air ruin the battery life? I have started to use my MacBook more often and I want to use my charger as it's main power source. (Noting that my battery is at 100%) It says "Power Source: Power Adapter". Does that mean that the MacBook is taking the power directly from the charger or is the charger charging battery then taking the power from there?
MacBook
It's a bit complicated. The power adapter itself is inadequate to supply peak power demands. If it demands more power than can be supplied a notebook computer will just shut down - I've seen it once. However, the battery can provide multiple times the power of the power adapter and can usually supply peak power on its own.
If you're usually not at power demands beyond the power adapter, then what would typically happen with leaving it plugged in would a repeated procedure. If it's under 95% then it would charge up the battery to 100%, then stop charging. The battery will then drop from self-discharge and supplemental power (if you do something that spikes the power temporarily). Once it goes below 95% it will start charging again in one stroke to 100%. So this way it's not constantly trying to top off the charge.
They might also mask this (like with iPhones) on some of the newer Macs. I know all my Macs from the 2001 iBook G3 to my mid-2012 MBP show it where I can see it at that 95-100% state, but my wife's new MBA seems to show 100% all the time when plugged in. I believe 100% could represent anything from 95%-100% in that case.
It's a bit complicated. The power adapter itself is inadequate to supply peak power demands. If it demands more power than can be supplied a notebook computer will just shut down - I've seen it once. However, the battery can provide multiple times the power of the power adapter and can usually supply peak power on its own.
If you're usually not at power demands beyond the power adapter, then what would typically happen with leaving it plugged in would a repeated procedure. If it's under 95% then it would charge up the battery to 100%, then stop charging. The battery will then drop from self-discharge and supplemental power (if you do something that spikes the power temporarily). Once it goes below 95% it will start charging again in one stroke to 100%. So this way it's not constantly trying to top off the charge.
They might also mask this (like with iPhones) on some of the newer Macs. I know all my Macs from the 2001 iBook G3 to my mid-2012 MBP show it where I can see it at that 95-100% state, but my wife's new MBA seems to show 100% all the time when plugged in. I believe 100% could represent anything from 95%-100% in that case.
John Galt wrote:
The latter. A portable Mac always draws its power from its battery.
Sure about that? I've literally seen it go through the 100-95% cycle for a week and I know it wasn't charging the battery. I'm at 98% right now. Looking at coconutBattery right now, and it's indicating a battery usage of 0 watts and connected. System Report > Hardware > Power indicates it's not charging and Amperage reads 0 mA. I'm pretty sure that it's telling me that it's not drawing power from the battery.
gtk64 wrote:
Will leaving my MacBook charger plugged in into my MacBook air ruin the battery life?
Yes, if you were to leave it connected literally all the time.
MacBook batteries need to be used, so be sure to use it at least occasionally. Once a week, perhaps, at a minimum. If you plan on keeping your Mac for a long time (and who doesn't) it's likely you will need to replace it once, but only once. That's been my experience. It's just as likely that event will occur shortly before Apple decides to render it "vintage" and no longer eligible for service from an Apple retail store. If and when that happens other options will remain available.
Budget about 50¢ a week for battery depreciation and you'll have more than enough to have Apple replace it, when required.
Read About Mac notebook batteries - Apple Support.
Does that mean that the MacBook is taking the power directly from the charger or is the charger charging battery then taking the power from there?
The latter. A portable Mac always draws its power from its battery.
Leaving the charger plugged in.
