Macbook pro, how to treat the battery ?

Hi,

I recently switched to Mac from PC ,so please be excused if this is a silly question .

Question -
Am I supposed to take the laptop off from mains when it gets fully charged? or should I keep using it on the mains when I can?

You can be absolutely safe using the laptop while still plugged in and fully charged, it would be good to drain the battery from time-to-time (i'm talking once every 1 or 2 months though)
The battery gets charged at a trickle rate for the last 15-20% anyway so there isn't any harm what-so-ever.

Hope this helps

- Simon

Thanks

I have been taking it off from mains after each full charge all this time .

Yep - when the battery's charged, leave it plugged in. In fact, plug it in whenever you can to keep the battery heavy. Like every modern laptop nowadays, the MBP has a Li-ion battery, which is monitored by a dedicated charging chip. It's impossible to overcharge or overdischarge it, and once fully charged, its voltage is monitored so a small trickle of power can be applied when it drops through self-discharge.

The reason you need to cycle it every so often is in fact nothing to do with the battery and its health - in fact, fully discharging and charging a Li-ion battery isn't good for it. It's done to calibrate the battery's 'fuel gauge', so it knows what the discharged state voltage is in order to give you a more accurate percentage. Apple's recommendation is to run the laptop until it forces itself into sleep mode, and then leave it overnight to fully discharge. Then plug it in and charge it fully, without disconnecting power.

mini998 said:

I have been taking it off from mains after each full charge all this time .

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Doing that will shorten your battery life. There are only a finite number of full charge cycles before your battery is weakened and doesn't hold a full charge for very long. At that point it becomes dependent on being plugged in all the time.
There is no harm in running on battery power when on the bus or at the coffee shop or whatever. Don't stress over it. Just be sure to keep up on the monthly maintenance suggested here. Apple Portables: Calibrating your computer's battery for best performance

Well what I've been doing is keeping it plugged in whenever I'm using it. If I'm taking it somewhere and I won't be there long, I'll go ahead and just take it without the charger. If I'm at my desk or at a place for a long time, I'll bring a charger or something.

Once the battery is fully charged, it will stay charged and will just run of the adapter. Keep it this way for extended periods of time to lower the overall use of the battery. Whenever I turn it off or put it to sleep however, I remove the cable and don't leave it plugged in.

I'm at 561 cycles right now and the battery health ranges from the mid 80s up to 90 percent which is very good seeing as the computer was purchased in 08.

That's odd - I had posted an almost identical question - about 12 hours earlier...

Yet - it gained zero responses !
How odd - is it the time difference I wonder ?

Young Spade said:

Whenever I turn it off or put it to sleep however, I remove the cable and don't leave it plugged in.

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Why? In sleep mode, the computer still uses a fair amount of power, draining the battery slowly. It's better to keep it plugged in to prevent cycling it unecessarily.

And yeah, looking after the battery and using the adaptor whenever possible makes it live much longer. Obviously it's a portable machine so use it on the battery when you need to of course!

In that other nether-world the majority still inhabit - the advice I had was to fully charge the battery - then remove it - if most of your work is done at home or near a power socket etc

Not the same for Mac notebooks then it seems...

Power management on these machine are pretty darn good, so no need to worry, and the management is getting better all the time.

- Simon

pedropete said:

In that other nether-world the majority still inhabit - the advice I had was to fully charge the battery - then remove it - if most of your work is done at home or near a power socket etc

Not the same for Mac notebooks then it seems...

Click to expand...

Sorry, but it's exactly the same for PC and Macs. Both use Li-ion battery packs with an internal protection board (and probably the same brand of cells!), and both have smart battery charge management controllers on the motherboard.

In fact, I wouldn't be surprised if many other laptops use the same ST Micro chip as the Macbook.

Anything with a Li-ion battery should be charged whenever possible. That goes for iPhones and other mobile phones and all laptops/Macs built within the last 15 years...

pedropete said:

In that other nether-world the majority still inhabit - the advice I had was to fully charge the battery - then remove it - if most of your work is done at home or near a power socket etc

Not the same for Mac notebooks then it seems...

Click to expand...

Yea you definitely don't want to do this. With MBs (and I assumed all laptops) the battery needs to be plugged. Have you ever been working off of the charger and look up to see it has some time left before it's fully charged again? As if it lost charge and is going back up?

When the computer needs more power than the charger can provide it will pull from the battery. Because you removed the battery, the computer will throttle its performance to ensure that you won't have any outside drain.

Apple has a great site for how to maintain and use your batteries properly for all of their devices:

Apple - Batteries

In addition, you'll find a lot of great information by searching here at Mac-Forums. There are many threads out there that you'll find useful on this subject:

Mac-Forums.com - Search Forums

Young Spade said:

Yea you definitely don't want to do this. With MBs (and I assumed all laptops) the battery needs to be plugged. Have you ever been working off of the charger and look up to see it has some time left before it's fully charged again? As if it lost charge and is going back up?

Click to expand...

Nope. This is because when the battery is charged, the management circuit cuts off power to it completely and since over time, the battery discharges by itself so the computer applies what's called a "topping charge" when it drops below the low fully-charged threshold. Li-ions can't be trickle charged.

So once the battery hits 100%, the computer stops charging it. When it drops by itself through self-discharge to 98% (this is just an example), it will charge once again until 100%. IBM Thinkpads have a handy utility which lets you view battery voltage and charge current; it shows this happening very nicely. Don't think there's one for Apple hardware though.

Young Spade said:

When the computer needs more power than the charger can provide it will pull from the battery. Because you removed the battery, the computer will throttle its performance to ensure that you won't have any outside drain.

Click to expand...

No laptops do this. It would be incredibly bad design as the computer would be unable to run at full speed with a battery that's reached the end of its useful life. I'm afraid that's a myth - no Li-ion management chips will do this.


Extra note: self-discharge is one reason why the battery's voltage drops after a full charge, but it's also because of the surface charge effect, present in an extent in lead-acid batteries too. Macbooks fast-charge (high current) the battery up until 80%, and then slowly fill the rest for proper end-of-charge termination detection. However, when fast-charged, the chemical reaction happens slightly faster at the edges of the plates - when left to sit for a 10 mins or so, the reaction spreads to the centre, decreasing nominal voltage.

It's why if you crank your car until the battery no longer turns the starter motor and then try again in half an hour, it seems to regain a bit of life.

Hope this helps!

Conflicting statement by Apple?

On this page, Apple Portables: Calibrating your computer's battery for best performance, Apple includes this statement: "Current Apple portable computer batteries are pre-calibrated and do not require the calibration procedure outlined in this article."

Is that to be believed? I'm in the midst of my first calibration on my brand new MBP15 (10.6.8), and I'm inclined to think it doesn't mean quite what it says. The other pages I've seen on the subject seem to be consistent in their advice to do this regularly, and early for a new Mac, such as mine.

Mac OS X 10.6 Help: Calibrating a portable computer battery
Mac OS X 10.4 Help: Calibrating a MacBook or MacBook Pro battery

My guess, since the first article is from July of this year - they're telling you that new machines have had the batteries calibrated and there is no longer a need to do a calibration during the first week.