Is it ok to leave MacBook Air plugged in all the time?

Yes, leave it plugged in and use Optimized Charging. Your battery will not be overcharged and charging is managed by the system Once it determines you leave it plugged in it will charge to 80% and remain on Hold. If you don't leave it plugged in, you are just unnecessarily increasing your Battery Cycles that will result in reduced battery life when you really need it.

xWauwau wrote:

Not a critique, just wanted to ensure Mgud doesn’t result in being surprised about 200 charging cycles while always having it plugged in.

I would add on to what BobTheFisherman notes and say the Battery Cycles are dramatically reduced when left plugged in. It is actually the discharge that accumulates a single battery cycle when it has reached an accumulation of 100% of the charge.

On occasion the Mac will still use battery power when plugged in and is the normal operation of Optimized Charging. On my Mac, charging will be on hold at 80% and about once every week will charge to 100% for battery recalibration, then drop back down to 80% on battery power. That means that the battery will have discharged by 100% in about 5 weeks resulting in a single charge cycle. Compare that to the amount of charge cycles that would have occurred over the 5 weeks without it being plugged in.

I have 141 charge cycles on a 6 year old Mac that mostly has been left plugged in, but I do take in on vacation where additional charge cycles were needed. At that rate I have 2 more years before I would even see the 200 charge cycles you mentioned and that would be over 8 years.

In addition to the article from Apple itself linked in another post, my personal opinion is based off the following:

it shouldn’t be a problem for itself to leave your MacBook plugged in, but, the battery seems to keep its best health not being charged full, optimal is ≈80%, based off all the features apple provides with their products, like charging the iPhone battery up to 80% until you need it again, or only charging to 80% at all. A useful tip also would be, if checking on apple support website, they estimate a cost of $0 for battery replacement if you have an apple care + plan. I do not know however, if this includes shipping and the usual other costs coming with such a service.

梁181 wrote:

even without optimized charging will the power goes directly to the mainboard after the battery is fully-charged

Yes, your battery will not be overcharged. Generally lithium batteries prefer to be at a 80% state compared to being at 100%, but there has been no documentation or trials to show if the battery will simply last a couple months longer or not.

You may want to review this article.

Batteries - Maximizing Performance - Apple

Mac Jim ID wrote:

If you don't leave it plugged in, you are just unnecessarily increasing your Battery Cycles that will result in reduced battery life when you really need it.

In my understanding, battery cycles do not have anything to do with the MacBook being plugged in or not. Viewed logically, the machine will use electricity, while it is charging at the same time, resulting in not losing charging level, though the electricity is still going through the battery. You can test it, and I believe it to be explained at the Apple website as well (linked by downstairsdave), as you leave the MacBook plugged in while using it, it will still accumulate charging cycles. Not a critique, just wanted to ensure Mgud doesn’t result in being surprised about 200 charging cycles while always having it plugged in.

xWauwau wrote:

Mac Jim ID wrote:

If you don't leave it plugged in, you are just unnecessarily increasing your Battery Cycles that will result in reduced battery life when you really need it.

In my understanding, battery cycles do not have anything to do with the MacBook being plugged in or not. Viewed logically, the machine will use electricity, while it is charging at the same time, resulting in not losing charging level, though the electricity is still going through the battery. You can test it, and I believe it to be explained at the Apple website as well (linked by downstairsdave), as you leave the MacBook plugged in while using it, it will still accumulate charging cycles. Not a critique, just wanted to ensure Mgud doesn’t result in being surprised about 200 charging cycles while always having it plugged in.

The rate of accumulation of battery cycles is reduced when leaving the computer plugged in.

But, you get my point, right? Maybe I don’t understand this correctly, but from the sentence ”You complete one charge cycle when you’ve used (discharged) an amount that represents 100% of your battery’s capacity”, I personally conclude that if you’ve used around 100% of your Mac’s battery, it will have completed one charging cycle, and so I would initially see the cause of the low amount of cycles your MacBook seems to have accumulated is caused by low-power usage, and not the fact that it’s plugged in. The only reason, and I don’t know if this is how it works or not, why leaving it plugged in would help, is the electricity not going through the battery when using the MacBook, but getting directly passed through to the power-consuming component. If you have info that this is the case, I’d be happy to be corrected.

even without optimized charging will the power goes directly to the mainboard after the battery is fully-charged

xWauwau wrote:

But, you get my point, right? Maybe I don’t understand this correctly, but from the sentence ”You complete one charge cycle when you’ve used (discharged) an amount that represents 100% of your battery’s capacity”, I personally conclude that if you’ve used around 100% of your Mac’s battery, it will have completed one charging cycle, and so I would initially see the cause of the low amount of cycles your MacBook seems to have accumulated is caused by low-power usage, and not the fact that it’s plugged in. The only reason, and I don’t know if this is how it works or not, why leaving it plugged in would help, is the electricity not going through the battery when using the MacBook, but getting directly passed through to the power-consuming component. If you have info that this is the case, I’d be happy to be corrected.

Read the previous responses.

Thanks for clearing this up.