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View Full Version : "Proper" Battery Usage for New MBA? Aka Power Supply vs. Battery




Blazer5913
Nov 29, 2010, 09:28 AM
Hello all. As I just bought a 13" MBA, I am still in my "babying" phase of the machine and want its battery power/capacity to last as long as possible. I have already done the battery calibration recommended by Apple (not even sure if its 'necessary' but I did it anyways), with charging, resting, draining, resting, and re-charging. But now I am worried about the battery cycles. Should I only plug my MBA in when the battery is close to being drained (aka use it on battery power for most of my usage?) or is it okay to drain the battery to like 80% remaining, charge, and then drain to 70% remaining, then charge again? Im not sure if Im making sense, but basically I don't want to be wasting these valuable cycles, as they seem to determine battery health and longevity. So what is the proper battery usage for the MBA, or is it basically use off power when you want and use on power supply when its available? thanks



powerbook911
Nov 29, 2010, 09:43 AM
Honestly, the batteries and chargers are better now.

However, one thing that I did find killed my older notebook batteries without question:

Leaving it plugged into the A/C. If it's just sitting on your desk or whatever charging, when it's done, go ahead and unplug it (not immediately, but don't just leave it plugged in days or weeks).

Furthermore, just using the machine on a regular basis, not always having it fully charged, or fully drained, is good for it. Keep the energy in it moving.

Overall, I wouldn't stress it. Just enjoy your machine. However, the one thing I do recommend as I said, just don't leave it plugged in all day , every day.

Blazer5913
Nov 29, 2010, 09:46 AM
Okay, so you would recommend to plug it in when charging, obviously, and also while I am actually doing work on my MBA when its on my desk near the AC charger. Yet, when I'm not using it (just say during the day when I'm at work) and it has fully charged overnight, then unplug it and let it sit there? Thanks

Honestly, the batteries and chargers are better now.

However, one thing that I did find killed my older notebook batteries without question:

Leaving it plugged into the A/C. If it's just sitting on your desk or whatever charging, when it's done, go ahead and unplug it (not immediately, but don't just leave it plugged in days or weeks).

Furthermore, just using the machine on a regular basis, not always having it fully charged, or fully drained, is good for it. Keep the energy in it moving.

Overall, I wouldn't stress it. Just enjoy your machine. However, the one thing I do recommend as I said, just don't leave it plugged in all day , every day.

alust2013
Nov 29, 2010, 09:47 AM
I wouldn't worry about it too much. The battery is supposed to last for 1000 cycles. That's a lot, basically 3 years if you have a full cycle almost every day, which is not likely. Personally I just leave mine plugged in primarily, and use the battery down to at least 50% every 3 days or so, and I have 97% health still after about 170 cycles, which is quite good.

aristobrat
Nov 29, 2010, 09:53 AM
It's OK to use it so that it drains down to 70%, and then charge it back up. That would count as 30% of a cycle, not a whole cycle.

Personally, I don't needlessly use the battery when plugging in isn't a hassle, but I'm not paranoid about cycles enough to chose not to use my Air on battery power when that would be more convenient.

The worse thing you can do for any battery is to leave it plugged in 100% of the time. You don't have to worry about unplugging your Air after it fully charges. Just don't leave it plugged in for literally an entire month.

I know you've said you've read this, but for anyone that hasn't, Apple has a good explanation of how to best handle your notebook batteries. It's pretty much everything powerbook911 covered.
http://www.apple.com/batteries/notebooks.html

jimboutilier
Nov 29, 2010, 09:56 AM
Calibrate the battery periodically (once to a few times a year) so it continues to display accurate battery life. Use it on AC when available and charge it when it when you have to.

A lot of factors go into bettery longevity, but a battery has only so many cycles in it. I have not seen specs for the new MBA but past ones were warrantied for 750-1000 cycles if memory serves. A slight drain and recharge will not count as a cycle. So you can get away with brief periods off AC without going back on costing you a cycle.

But remember you bought a MBA for it's mobility and tethering it to AC all the time kind of defeats the purpose. So use it however works best for you balancing onvienence and longevity. Again have not seen pricing for the current MBA but you could have apple replace the battery in previous MBAs for about $100. If you about drained it every day you'd still likely get close to three years out of the battery - and if not and it was within the warranty cycles Apple would likely replace it at no cost.

So while you don't want to squander cycles where AC is readily available, make use of it's mobility using battery where you need to and recharging where you can (keeping in mind once you drop below a cirtian point it's going to cost you a cycle so you might as well drain it unless you need a quick recharge to be off AC later in the day for an extended period of time).

tmoerel
Nov 29, 2010, 12:28 PM
Honestly, the batteries and chargers are better now.

However, one thing that I did find killed my older notebook batteries without question:

Leaving it plugged into the A/C. If it's just sitting on your desk or whatever charging, when it's done, go ahead and unplug it (not immediately, but don't just leave it plugged in days or weeks).

Furthermore, just using the machine on a regular basis, not always having it fully charged, or fully drained, is good for it. Keep the energy in it moving.

Overall, I wouldn't stress it. Just enjoy your machine. However, the one thing I do recommend as I said, just don't leave it plugged in all day , every day.

Well...my experience is totally different. I had a white macbook for more than 3 years and it was almost always on a charger. The battery is now still at 85% of its original capacity which in my opinion is very good. The thing is, the more it is on the charger the less it charges. Once full it doesn't get charged any more.
With LiIon/LiPo batteries it is the number of charge cycles which limit the life of the battery so try to minimise these cycles by keeping plugged in when possible.

GGJstudios
Nov 29, 2010, 12:33 PM
This should answer most, if not all, of your battery questions: Apple Notebook Battery FAQ (http://forums.macrumors.com/showpost.php?p=9875442&postcount=23)

zstar
Nov 29, 2010, 09:29 PM
Hmm, I guess I am similarly worried about my Macbook Air's battery as the OP. One question that I cannot seem to find definite, conclusive answers is whether the computer draws from AC power when it is fully charged. (i.e. when the battery is 100% and you continue using the computer, does it draw power from the AC power source directly or does it draw from the battery and the charger constantly replenishes the battery?)

There also don't seem to be conclusive answers for the OP's question, some say leaving it plugged in all the time damages the battery, some say it is good for the battery because no charge cycles are used.

Argh, I hate batteries now. :o

GGJstudios
Nov 29, 2010, 09:37 PM
Hmm, I guess I am similarly worried about my Macbook Air's battery as the OP. One question that I cannot seem to find definite, conclusive answers is whether the computer draws from AC power when it is fully charged. (i.e. when the battery is 100% and you continue using the computer, does it draw power from the AC power source directly or does it draw from the battery and the charger constantly replenishes the battery?)

There also don't seem to be conclusive answers for the OP's question, some say leaving it plugged in all the time damages the battery, some say it is good for the battery because no charge cycles are used.
It draws from AC power, unless the power demands briefly exceed the power available from AC, in which case, it also draws from the battery. Read the FAQ link I posted, especially the last section on AC Power. The answers are there.

zstar
Nov 29, 2010, 09:47 PM
It draws from AC power, unless the power demands briefly exceed the power available from AC, in which case, it also draws from the battery. Read the FAQ link I posted, especially the last section on AC Power. The answers are there.

I could not find the answer for the AC/Battery when fully charged issue in the FAQ, including the last section, and so was simply looking for additional information from other members. I have indeed read the Macrumors FAQ twice before I saw this thread.

Anyway, thanks for your help, it has cleared at least one of my misconceptions and worries about the batteries in apple notebooks.

GGJstudios
Nov 29, 2010, 10:00 PM
I could not find the answer for the AC/Battery when fully charged issue in the FAQ, including the last section,
It's there:

Also, it is not recommended to run your Mac on the AC adaptor with the battery out (http://support.apple.com/kb/HT2332) (Of course, this only applies to removable batteries).
From that link:
If the battery is removed from a MacBook or MacBook Pro, the computer will automatically reduce the processor speed. This prevents the computer from shutting down if it demands more power than the A/C adaptor alone can provide.

Over Achiever
Nov 29, 2010, 10:05 PM
@GGJstudios But you can't remove the battery from the new Macbook Airs, so how does that apply? Shouldn't the AC adapter provide enough power for the MBA when plugged in? I can understand when say the 45W adaptor is plugged into a 17" MBP or something.

zstar
Nov 30, 2010, 04:22 AM
It's there:

From that link:

Yes, I realise that but like what Over Achiever is saying, I fail to see how that can be applied to the Macbook Air as it has a non-removable battery.

Regarding the quoted text from the apple support document, it also does not state specifically the Macbook Air. Thus, I find the article a little vague and would probably not have happened to see the answer to my queries with a quick read-through as opposed to an article that simply stated "The Macbook Air(or any computer with a non-removable battery) runs on AC Power when fully charged."

GGJstudios
Nov 30, 2010, 06:16 AM
@GGJstudios But you can't remove the battery from the new Macbook Airs, so how does that apply?
..I fail to see how that can be applied to the Macbook Air as it has a non-removable battery.
Yes, I know the MBA, like the newer MBPs, have non-removable batteries. The point is that there are situations where it is necessary to draw on both AC and battery power. Most of the time, your MBA will run on AC power when plugged in, but it CAN draw on the battery, as well.
One question that I cannot seem to find definite, conclusive answers is whether the computer draws from AC power when it is fully charged. (i.e. when the battery is 100% and you continue using the computer, does it draw power from the AC power source directly or does it draw from the battery and the charger constantly replenishes the battery?)
From Apple Portables: Battery may not show a full charge in Mac OS X (http://support.apple.com/kb/TS1909), which is also referred to in the FAQ I posted:
Some Apple portable computers (PowerBook G4, iBook, MacBook Pro, MacBook, and MacBook Air) may not show the battery as 100 percent charged in Mac OS X, even when the power adapter is connected.

The battery may appear to stop charging between 93 percent and 99 percent. This is normal. The batteries used in these computers are designed to avoid short discharge/charge cycles in order to prolong the overall life of the battery.