Declining Battery Capacity

Verdanice · Jun 14, 2008

Hey,

I picked up my Macbook Pro in September of last year, making it about 9 1/2 months old. It's plugged in much of the time I use it, but I do take it off the power source on a regular basis. I've noticed the battery draining more quickly lately, so I took a look at the capacity reading. Here it is (from Coconut):

It's at 73%. This is after a full calibration last night, where before that it read 70%. I normally calibrate approximately every two months as recommended. I do recall the reading being in the high eighties no more than four months after getting the system, which seemed somewhat odd.

I've read up on some experiences with the MBP battery, but most mentions were regarding defective models acknowledged and recalled by Apple. I read at one point that a battery below 75% (or thereabouts) capacity with less than 300 cycles would be covered under warranty. Also, Apple states here (bottom right column) that the battery should retain 80% capacity after 300 cycles (but it does not go on to discuss the warranty). That said, here are my battery specs from the System Profiler:

As you can see, I'm at 160 battery cycles currently - with a battery status of 'check battery'. I can't seem to find a solid answer as to what that means (not even on Apple's site).

So, think I can get a replacement out of this? Is my battery of a model known to be touchy? I've heard that about Sony's in general, but I'm not sure if that's accurate.

Thanks for any help you can offer!

shmutheprophet · Jun 14, 2008

What does "calibrating" mean?

Verdanice · Jun 14, 2008

shmutheprophet said:
What does "calibrating" mean?

It's a process of charging and discharging your notebook battery that helps keep it running at the highest capacity it can. It prolongs the life of your battery. Apple describes how to do it for the MB and MBP here.

stiphone · Jun 15, 2008

Mmmm...you brought out an interesting question. I heard some time ago about defect batteries and Apple replacing it. Mine's worse of now. It's only at 29% after 55 battery-loadcycles. Think i'll give Apple a call tomorrow and see if i'm eligible for replacement on this battery. Thanks for bringing this out!!

motulist · Jun 15, 2008

Verdanice said:
It's a process of charging and discharging your notebook battery that helps keep it running at the highest capacity it can. It prolongs the life of your battery. Apple describes how to do it for the MB and MBP here.

Incorrect*. Calibrating means calibrating the battery METER to help your Mac give a more accurate reading of remaining battery time left, but it does not help your battery capacity. The more you use your battery, the less capacity it will be able to hold in the future. So doing a calibration will actually reduce your battery's capacity.

* = this is all AFAIK. Even though the Apple page you linked says that that's the purpose of calibration, everything else I've read about lithium ion battery calibration says otherwise.

BatteryUniversity.com said:
Although lithium-ion is memory-free in terms of performance deterioration, batteries with fuel gauges exhibit what engineers refer to as "digital memory". Here is the reason: Short discharges with subsequent recharges do not provide the periodic calibration needed to synchronize the fuel gauge with the battery's state-of-charge. A deliberate full discharge and recharge every 30 charges corrects this problem. Letting the battery run down to the cut-off point in the equipment will do this. If ignored, the fuel gauge will become increasingly less accurate. (Read more in 'Choosing the right battery for portable computing', Part Two.)

http://www.batteryuniversity.com/parttwo-34.htm

DoFoT9 · Jun 15, 2008

OP, do you discharge and recharge (fully) every cycle?

scienide09 · Jun 15, 2008

Apple's usual policy is that if the fully charged battery holds less that 80% of the original battery capacity, AND if there are less than 300 cycles on the battery, they will usually replace it.

Are you still within warranty? Call Apple or take it to your local Genius.

skye12 · Jun 15, 2008

motulist said:
Incorrect*. Calibrating means calibrating the battery METER to help your Mac give a more accurate reading of remaining battery time left, but it does not help your battery capacity. The more you use your battery, the less capacity it will be able to hold in the future. So doing a calibration will actually reduce your battery's capacity.

* = this is all AFAIK. Even though the Apple page you linked says that that's the purpose of calibration, everything else I've read about lithium ion battery calibration says otherwise.

http://www.batteryuniversity.com/parttwo-34.htm

Correct, it just calibrates the meter, which usually overstates the remaining battery life.

I think its better to not discharge the battery anymore than is necessary.

motulist · Jun 15, 2008

DoFoT9 said:
OP, do you discharge and recharge (fully) every cycle?

You misunderstand what the term "cycle" means. A cycle means the battery expending the amount of energy that can be stored in it's full charge capacity. It doesn't matter if you run a fully charged battery down to nothing in one shot, or use up half the battery's charge then plug it back in to recharge it fully and then use up half the battery's charge again. Both of those scenarios use up just one full cycle of the battery.

DoFoT9 · Jun 15, 2008

motulist said:
You misunderstand what the term "cycle" means. A cycle means the battery expending it's full charge capacity. It doesn't matter if you run a fully charged battery down to nothing in one shot, or use up half the battery's charge then plug it back in to recharge it fully and then use up half the battery's charge again. Both of those scenarios use up just one full cycle of the battery.

i did not misunderstand, i just worded incorrectly.

what i should have said it:

OP: when you use your battery do you fully discharge and then recharge as often as possible?? this will help to increase battery capacities to the highest levels, giving the longest possible battery run time and longer longevity. (if that even makes sense...)

im well aware that you can use up 50% then charge fully and use 50% again that it is still counted as a "cycle", i just worded incorrectly.

motulist · Jun 15, 2008

skye12 said:
Correct, it just calibrates the meter, which usually overstates the remaining battery life.

So I was correct about the other poster being incorrect.

skye12 said:
I think its better to not discharge the battery anymore than is necessary.

I agree completely. Unless having an accurate report about how much battery time remaining is important to you, then you should never calibrate your battery. Lithium ion batteries should be kept plugged in as often as is convenient.

motulist · Jun 15, 2008

DoFoT9 said:
when you use your battery do you fully discharge and then recharge as often as possible?? this will help to increase battery capacities to the highest levels, giving the longest possible battery run time and longer longevity. (if that even makes sense...)

Well then perhaps you're wording your statement wrong again, because deep discharging is exactly the OPPOSITE of what you should do with lithium ion batteries.

BatteryUniversity.com said:
Avoid frequent full discharges because this puts additional strain on the battery. Several partial discharges with frequent recharges are better for lithium-ion than one deep one. Recharging a partially charged lithium-ion does not cause harm because there is no memory. (In this respect, lithium-ion differs from nickel-based batteries.)

- http://www.batteryuniversity.com/parttwo-34.htm

DoFoT9 · Jun 15, 2008

motulist said:
...

I agree completely. Unless having an accurate report about how much battery time remaining is important to you, then you should never calibrate your battery. Lithium ion batteries should be kept plugged in as often as is convenient.

i STRONGLY have to disagree with you there.

my dad fully dischagred and recharged his ibook battery as much as he could (literally every time). he ended up getting about 655 cycles before he decided to get a new one.

i on the other hand have not gotten past 150 cycles and i constantly have mine plugged in on the power overnight and during the day. my battery capacity is way lower than his and it declines faster than his does.

DoFoT9 · Jun 15, 2008

motulist said:
Well then perhaps you're wording your statement wrong again, because deep discharging is exactly the OPPOSITE of what you should do with lithium ion batteries.

- http://www.batteryuniversity.com/parttwo-34.htm

aaahh but i never said deep discharging did i??

motulist · Jun 15, 2008

DoFoT9 said:
aaahh but i never said deep discharging did i??

It sure seemed like you did. You said fully charging and fully discharging (known as a deep discharge) will help keep up your battery's capacity. Perhaps that wasn't what you meant to say. As shown in the link I've provided, it specifically in no uncertain terms that lithium ion batteries should be kept plugged in as often as possible.

DoFoT9 · Jun 15, 2008

motulist said:
You said fully charging and fully discharging (known as a deep discharge) will help keep up your battery's capacity. Perhaps that wasn't what you meant to say.

eh silly mistake, people identify things by different names, i refer to fully charging/discharging as making it go flat until the computer goes to sleep. i refer "deep discharging" to "calibrating"... mybads

motulist · Jun 15, 2008

DoFoT9 said:
eh silly mistake, people identify things by different names, i refer to fully charging/discharging as making it go flat until the computer goes to sleep. i refer "deep discharging" to "calibrating"... mybads

A deep discharge means running your battery until it's almost empty, regardless of the amount of charge it started with. Lithium ion batteries should NOT be deep discharged on purpose. Lithium ion batteries should always be kept plugged in when possible. They should be kept as fully charged as possible for as long as possible.

Definition of "deep charge"

DoFoT9 · Jun 15, 2008

motulist said:
A deep discharge means running your battery until it's almost empty, regardless of the amount of charge it started with. Lithium ion batteries should NOT be deep discharged on purpose. Lithium ion batteries should always be kept plugged in when possible and kept as fully charged as possible for as long as possible.

http://www.google.com/search?num=10...m=0&ct=result&cd=1&q="deep+discharge"&spell=1

yes, because i will keep my battery always plugged in even while sleeping so that it can overcharge/melt down

motulist · Jun 15, 2008

DoFoT9 said:
yes, because i will keep my battery always plugged in even while sleeping so that it can overcharge/melt down

I don't understand, are you trolling, or are you really this misinformed? Lithium ion laptop batteries will never overheat or melt from being overcharged. Once fully charged, the computer will stop sending them electricity.

DoFoT9 · Jun 15, 2008

motulist said:
I don't understand, are you trolling, or are you really this misinformed? Lithium ion laptop batteries will never overheat or melt from being overcharged. Once fully charged, the computer will stop sending them electricity.

not true, the battery will continue to be charged and discharged, it is constantly going through cycles.

when the battery is charged it will be used about 5%, then be charged again. this inevitably means that after 20 of these little sections of time has passed, you have used an additional cycle.

motulist · Jun 15, 2008

DoFoT9 said:
not true, the battery will continue to be charged and discharged, it is constantly going through cycles.

when the battery is charged it will be used about 5%, then be charged again. this inevitably means that after 20 of these little sections of time has passed, you have used an additional cycle.

if it wasn't good for the battery, then that's not how they would make it work. Do you have a source citation for your claim?

DoFoT9 · Jun 15, 2008

motulist said:
Do you have a source citation?

i was just looking for it, unfortunately not, i had a massive argument with a fellow MR member here that provided me with the sources, if only i could find that page.

alphaod · Jun 15, 2008

motulist said:
if it wasn't good for the battery, then that's not how they would make it work. Do you have a source citation for your claim?

That is considered a full cycle and it's not about being good for bad for the battery; seriously Li-ion batteries in cell phones; who cares about cycling them all the time? Sure I cycle them once a month but who else does that?

Verdanice · Jun 15, 2008

Haha, alright, it would appear there's some uncertainty over the issue - and I've noticed that before. I don't have an opinion because I have not done the research, but apparently those who have all have different opinions anyways.

Anyways. I have to get my logic board, screen, and optical drive replaced in a couple weeks (dropping it of when I go on vacation), so I'll try to get them to drop a battery in there while they're at it. Maybe THIS will push them over the edge that lets them replace the damn system, it'd be a lot easier for everybody. They've already replaced my memory in the past.

jcroeth · Jun 17, 2008

First of all, to bring the thread back to the OP's topic...

Verdanice, you battery may be defective. If the battery is 9.5 months old and you have 160 load cycles that means you've had almost 17 load cycles a month, which means you almost certainly didn't damage it by leaving it plugged in too much. And as you said, you've calibrated it, so that's not the issue either.

It should still be under the 1 year warranty. I would call Apple about it for sure, especially if they publicize that the battery should retain 80% health up to 300 load cycles.

As for the other issues in this thread...

Lithium ion batteries should always be kept plugged in when possible. They should be kept as fully charged as possible for as long as possible.

This may seem intuitively correct, but in reality it is not the case. In fact it is the opposite.

From Battery University :

http://www.batteryuniversity.com/parttwo-34.htm

The worst condition is keeping a fully charged battery at elevated temperatures, which is the case with running laptop batteries. If used on main power, the battery inside a laptop will only last for 12-18 months. I must hasten to explain that the pack does not die suddenly but begins with reduced run-times.

From Apple :

http://www.apple.com/batteries/notebooks.html

For proper maintenance of a lithium-based battery, its important to keep the electrons in it moving occasionally. Apple does not recommend leaving your portable plugged in all the time.

About the issue of small discharges/charges...

Quote:
Originally Posted by DoFoT9 View Post
not true, the battery will continue to be charged and discharged, it is constantly going through cycles.

when the battery is charged it will be used about 5%, then be charged again. this inevitably means that after 20 of these little sections of time has passed, you have used an additional cycle.
if it wasn't good for the battery, then that's not how they would make it work. Do you have a source citation for your claim?

Actually very small (less than 5 or 10%) discharges/charges are not good for lithium ion batteries.

This is why your battery power will sometimes read less than 100%, but your magsafe adapter won't begin charging the battery. This is to protect the battery from a small charge.

From Apple :

http://docs.info.apple.com/article.html?artnum=88344

Some PowerBook G4, iBook, MacBook Pro and MacBook computers may not show the battery as 100 percent charged in Mac OS X, even when the power adapter is plugged in. The battery appears to stop charging between 93 percent and 99 percent. (PowerPC-based computers may stop charging between 95 and 99 percent; Intel-based computers may stop charging between 93 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.

If anyone is interested, see these threads where I've posted about the damage that can be caused by leaving an Apple notebook with a lithium ion battery plugged in all the time :

https://forums.macrumors.com/threads/500184/

https://forums.macrumors.com/threads/500099/

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