01-04-2011, 01:56 PM

Is it a general rule to unplug devices when they're charged so that the battery doesn't get over-loaded or does it depend on the device? Like I heard some devices will automatically stop drawing power once they reach the full limit. I was kind of under the impression all charging devices work like this but apparently not.

Does a MacBook work this way?

01-04-2011, 02:00 PM

No a MacBook does not work that way.

Apple - Batteries

01-04-2011, 04:30 PM

Originally Posted by Meteora

Is it a general rule to unplug devices when they're charged so that the battery doesn't get over-loaded or does it depend on the device? Like I heard some devices will automatically stop drawing power once they reach the full limit. I was kind of under the impression all charging devices work like this but apparently not.

Does a MacBook work this way?

I'll give you an example of a device that has a battery that gets charged...and always remains plugged in...it's called a UPS (Uninterruptible Power Supply):

Uninterruptible power supply - Wikipedia, the free encyclopedia



- Nick

01-04-2011, 04:49 PM

So the MacBook's battery doesn't stop drawing power even after it's fully charged? Because the battery on a Dell laptop does.

01-04-2011, 05:44 PM

Originally Posted by Meteora

So the MacBook's battery doesn't stop drawing power even after it's fully charged? Because the battery on a Dell laptop does.

The link I posted answers the question. Did you read it?

01-05-2011, 11:28 AM

I just did now and, I don't see the answer to that question. It just speaks of lithium ion batteries and how they work, not whether or not its ok to leave the laptop plugged in after it's reached 100%.

01-05-2011, 11:19 PM

For proper maintenance of a lithium-based battery, it’s important to keep the electrons in it moving occasionally. Apple does not recommend leaving your portable plugged in all the time. An ideal use would be a commuter who uses her notebook on the train, then plugs it in at the office to charge. This keeps the battery juices flowing.

Apple does not recommend keeping the battery plugged in 100% of the time only because you will not be letting the juices run occasionally, not because of fear of overcharging.
They give the example of during the commute to work using your notebook, and charging it while at work and then when leaving work using it on battery power.

This is allowing the juices to flow as when the notebook is on charger fully charged the batteries juices aren't flowing, meaning that it is running of mains power, just as is the case with iPhones, iPods, etc.

If you are using your notebook on mains power all the time, and if not letting it run off battery at all, it is recommended to calibrate the battery once a month.
This gets the juices flowing.

If there was a fear of overcharging, Apple would say do not keep the notebook plugged in once the battery charge is at 100% because it will overcharge, or damage the battery.

01-07-2011, 01:48 PM

Originally Posted by Meteora

I just did now and, I don't see the answer to that question. It just speaks of lithium ion batteries and how they work, not whether or not its ok to leave the laptop plugged in after it's reached 100%.

You obviously didn't read the whole thing.

01-07-2011, 04:41 PM

When Apple replaced my MacBook battery recently, I was advised to follow this procedure:

1) Charge the new battery to 100%
2) Allow it to drop to 50%
3) Charge it back to 100%
4) Run the battery right down until it dies, and leave it overnight to completely drain it.
5) Charge back up to 100% and then use as normal.

I always try to let my battery drain completely, and rarely charge it until it dies.




It was once explained to me by someone at Orange - that a phones battery is like a jar of jam, if you constantly top up the jar without emptying it first, what you get is a load of mouldy jam at the bottom! I guess that's the same philosophy for laptop batteries.....?

01-07-2011, 06:10 PM

Originally Posted by MacFanDan

It was once explained to me by someone at Orange - that a phones battery is like a jar of jam, if you constantly top up the jar without emptying it first, what you get is a load of mouldy jam at the bottom! I guess that's the same philosophy for laptop batteries.....?

That was true back in the "old days" when rechargeable batteries had the "memory effect" issue (I think nickel cadmium-batteries)...not so applicable with batteries that have been used in apple laptops for at least 4-5 years.

I've mentioned this before...I have my laptop plugged in 99.98% of the time...and I let it run on the battery for 1-2 hours/month. I still get 4.5-5 hours total runtime on a full charge (this is on a battery that's supposed to get 5 hours). My laptops battery is 2.5 years old.

- Nick