# Should I not be charging my Macbook Pro all the time?



## Uduckhead (Sep 27, 2006)

I had heard somewhere that charging something constantly is bad for the battery. I've been cautious with my Macbook Pro and unplug it when it's full charged. Is this necessary? What are the repercussions of charging 24/7? Thanks.


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## barhar (Sep 27, 2006)

'Should I not be charging my Macbook Pro all the time?' - correct.

'I' ... unplug it [MacBook Pro] when it's full charged. Is this necessary?' - no. Once a battery is fully charged, it may be trickle charged (a different form of charging).

It is necessary to fully discharge the battery - most of the time, if not always; before re-charging.

'What are the repercussions of charging 24/7?' - see above and below.

Charging the battery, using the Mac (but not fully discharging the battery),  charging the battery, using the Mac (but not fully discharging the battery) - over and over - will result in the inability of the battery to cycle properly. This may shorten the life of the battery, and most likely will degrade the battery's ability to fully charge.


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## Uduckhead (Sep 27, 2006)

So in other words I should charge it fully, unplug it, use it until the battery runs out, then charge it up again?


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## lurk (Sep 27, 2006)

Well, there are a couple of things you need to look at.  The number of cycles in your battery and a thing called the memory effect.

First as a gross over-simplification every time you charge and discharge your battery it wears out a little bit.  In fact you can imaging that your battery might only have say 1000 charge/discharge cycles in it.  And as you keep cycling the battery it will hold less and less power.  For instance mine presently has 627 cycles on it and it holds about 2/3's of the charge it used to.

So every time you cycle the battery it will be less powerful the next time.

The second effect is a thing called memory.  This is kind of like your battery getting used to stopping at a given point and then quitting early.  So if you always run it down 50% and then charge it after a while it will not be possible to run it down more than 50% and you have effectively lost half your battery.  In the old days this was very important, today we have better batteries.

Modern laptops generally use Lithium Polymer batteries, these batteries have very little memory effect.  I have been told that the effect is so small that it will be overshadowed by the loss of power for a given battery due to cycling.  So you do not have to run them down regularly like in the old days of NiCad and NiMH cells.

My answer, leave it plugged in when you can but don't sweat it.  In a couple of years when it starts to get a little creaky like mine buy a new battery and be happy.  Remember, your machine is there to serve you and no the other way around.


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## barhar (Sep 27, 2006)

'So in other words I should charge it fully, unplug it, use it until the battery runs out, then charge it up again?' - more or less, yes. 

But you can leave the MacBook Pro connected after it is fully charge, from time to time. 

Just allow the battery to full discharge, instead of constantly connecting the MacBook Pro to the AC / DC adapter.

You can remove the non-fully discharged battery, from the MacBook Pro, connect the portable to the AC / DC adapter, and use the portable. Later, disconnect the MacBook Pro, re-install the battery, and continue to power the portable from the battery - until it fully discharges.  Then repeat the recharging cycle.

Clarification:
01. To fully discharge a Lithium ion battery - does not imply 'discharge to 0 volts'; but, to the low battery level of the menu bar or third party application voltage indicator.
02. Others sources to view - ([1], [2], and [3]). Many of [3]'s web sites state that Lithium ion can be connected more often to it charging system (the AC / DC adapter) with less problems - noted with Nickel Cadmium and / or Nickel Metal Hydride batteries.


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## eric2006 (Sep 27, 2006)

Fully discharging the battery every use may put too much stress on the battery, not to mention being inconvenient. You may want to do that once every 3 months or so, but you don't need to do it every cycle, especially with Li-ons. If anything, it's better to charge back up when you hit around 60%. Laptop batteries are designed to be used - so don't be afraid to use them how you want. A heavily used battery will still last a year, or two. Replacement batteries are around 100 bucks. Not bad for a $2000 laptop.


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## Uduckhead (Sep 28, 2006)

Hmmm...ok. So, it sounds like I should unplug when fully charged, but not wait until the battery is dead to recharge?


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## barhar (Sep 28, 2006)

'... So, ...I should unplug when fully charged,' - you can; but, do not have to.
'... but not wait until the battery is dead to recharge?' - correct.

When a full battery charge has completed, the AC / DC adapter can remain connected.

From time to time, let the battery discharge (noting its value via the menu bar indicator and / or third part software), and then perform a full battery charge.


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## fryke (Sep 28, 2006)

Use it any way you want, i.e. leave it charging/charged. About once a month at least, use it until the battery's drained completely, i.e. ignore the warnings, don't put it to sleep but rather use it until it goes to sleep by itself. You must set the Energy Saver prefpane to letting it never sleep for that! (Else it might just go to sleep automatically when you go get another cup of coffee...) Then charge it fully (you can still use the machine) and do the discharging scheme a second time. Again charge it 'til full. Now go your normal way for another month.


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## Uduckhead (Sep 29, 2006)

Wow, cool, thanks guys.


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## symphonix (Sep 29, 2006)

There is no need to worry about memory effect, charge/discharge cycles, or unplugging once fully charged. The batteries used on modern laptops are Lithium-Ion, which have no memory effect at all. The procedures described date back to the use of Nickel-Cadmium batteries, which we were using right up until the late 90s.

The Li-Ion batteries in modern laptops, iPods, etc have no memory effect and an operating life of nearly ten years. No special procedures, such as "do not overcharge" or "recharge frequently" need to be observed.

Besides, your laptop has a power management chip that takes care of all of that - if overcharging were to be an issue, the PMU (Power Management Unit) will automatically stop the charging process.


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