Laptop Battery Guide
From Mac Guides
This is a guide for Apple laptop batteries. Please be aware that PowerBooks and iBooks, as they have different batteries, do not share the current battery expectations that MacBooks and MacBook Pros have.
Facts about your battery
Apple uses standard Lithium-ion batteries in its current lineup of consumer and professional notebooks. Apple makes use of two different batteries for its notebook lines; one is for the MacBook, and one is for the MacBook Pro. Please ensure that you are refering to the correct battery when ordering from apple.com.
How long will your battery last?
This is highly dependant on your usage, and the way in which you maintain your battery. Apple expects your battery to retain approximately 80% of its charge after about 300 full cycles. In newer MacBooks and MacBook pros (2009 and later), Apple claim that the battery can be used for around 1000 cycles (5 years of typical use).
What is "full cycle"?
A cycle is when the total battery power is less then 50% before it is recharged. The battery electronics monitor the status of the cells during use, and not cycling the battery at least once a week may cause the electronics to get false recordings. It is best to fully drain the battery before you charge it up again. Seeing a fully charged in your battery status monitor as 99% is a good indication to fully cycle your battery.
The following table gives a rough idea of life expectancy for different models:
|Mac Laptop||Maximum Capacity||Capacity at 80%|
|MacBook||5020 mAh||4016 mAh|
|MacBook Pro 15"||5500 mAh||4400 mAh|
|MacBook Pro 17"||6400 mAh?||5120 mAh?|
|iBook G4 12"||4600 mAh?||3680 mAh?|
|iBook G4 14"||5600 mAh?||4640 mAh?|
|Aluminium PowerBook G4 12"||4600 mAh?||3680 mAh?|
|Aluminium PowerBook G4 15"||4600 mAh?||3680 mAh?|
|Aluminium PowerBook G4 17"||5400 mAh||4320 mAh|
What this means
Your battery carries a certain maximum charge. Every time your fully deplete the power equal to one maximum charge, your battery has gone through one cycle. For example, if your battery has a maximum charge of 5000 mAh (milliamp Hour), and you use this charge once (all 5000 milliamp hours), then you will have used one cycle. If you don't use the entire charge at once (which is more likely, as most of us commute or need to charge our notebooks whenever we have the opportunity), the calculation remains fairly basic.
You have a fully charged battery (5000 mAh) and you use 2000 mAh in one sitting, charge it up back to 5000 mAh, and then use another 1000 mAh. How much have you used? The answer is 60% of one cycle. Why? 2000 mAh=40% of one cycle 1000 mAh=20% of one cycle Total=3000 mAh, or 60% of one cycle.
Thus, your battery goes through cycles on a fairly straight-forward basis; there is no need to fully deplete your battery every time.
What does 80% mean?
The expectation of an 80% retention for up to 300 cycles means that your battery will retain up to 80% of its maximum charge for the first 300 cycles. This is a rough guide that is based on an estimate of how much power loss your battery will experience over the course of a certain number of cycles.
Your battery, when it had 0 cycles, had a charge of 5000 mAh. After 300 cycles, your battery has 80% of its one-time maximum charge, or in other words, it now holds 4000 mAh (5000*0.8=4000)
So, you may be wondering how long you can expect your battery to last based on your usage. The best way to determine this is to find out how much you use your battery on a weekly or daily basis. Here are some sample estimates based on some expected use rates:
- 1 cycle (the full charge of your battery) every day will retain a maximum charge above 80% of the original for about 10 or 11 months. After this point, you will begin to notice that your battery no longer has the same amount of charge that it used to.
- 1 cycle every weekday (or 5 cycles per week) will last for about 14 months before the battery's maximum charge dips below 80%.
- 3 cycles every week will last for about 2 years before the battery's maximum charge dips below 80%
- 2 cycles every week will last for about 3 years before the battery's maximum charge dips below 80%
You should use these estimates to determine when to buy your new battery, or even if you need a new battery. As some users prefer desktop replacements, they probably won't need a new battery very often. Other users, however, are constantly on the go and need new batteries sooner. This is a decision you should base on your usage and needs.
How can I see my battery's age and condition?
You can easily check your battery's 'official' condition (accepted by Apple) from the Apple System Profiler (you can open it by going to Apple Menu > About This Mac, then clicking More Info). In the Apple System Profiler, in the Power section and under Battery check the Condition statement. A Good reflects a healthy battery where as a Check Battery means the battery is either defective (in case of under 300 cycles) or is unable to hold anymore charge (in case of more than 300 cycles).
Otherwise you can use third party applications which give you more information. The two most user-friendly are Coconut Battery and iStat Pro (Mac OS X 10.4 Tiger is needed for the latest versions of both).
This program will provide you with detailed information about your battery, including the mAh it once held, and its relative health (such as 75% of maximum charge, 90% of maximum charge, etc). It is easy to download and many find it to be very useful.
A Coconut Battery sample:
This is a widget for your Dashboard. It offers information about your computer's internal heat, fan speed, CPU usage, etc, but also includes a battery moniter. Users have reported that this program is less accurate, but it still has value as a second source of information. Both programs should provide somewhat similar information. If one offers an entirely different picture than the other, you may have a problem that needs attention.
∗These programs are not endorsed or supported by Macrumors.com. You download these at your own risk.
In order to see the correct battery information on your computer, you should perform routine battery calibrations about once per month. Due to changes between models, older notebook models, including iBooks, and most G4 PowerBooks, do not use the current calibration. If you have an iBook or PowerBook, go to Apple's page on battery calibration in order to determine the correct method of calibration for your model.
Intel notebooks, which includes all MacBooks and MacBook Pros, use the following method of calibration: 
- Plug in the power adapter and fully charge your laptop's battery until the light ring or LED on the power adapter plug changes to green and the onscreen meter in the menu bar indicates that the battery is fully charged.
- Allow the battery to rest in the fully charged state for at least two hours. You may use your computer during this time as long as the adapter is plugged in.
- Disconnect the power adapter with the computer still on and start running the computer off battery power. You may use your computer during this time. When your battery gets low, you will see the low battery warning dialogue on the screen.
- Continue to keep your computer on until it goes to sleep. Save all your work and close all applications when the battery gets very low, before the computer goes to sleep.
- Turn off the computer or allow it to sleep for five hours or more.
- Connect the power adapter and leave it connected until the battery is fully charged again.
Battery calibration will help your computer display accurate information, and will give you an accurate picture of your battery's relative health and ability to hold a charge. If you believe that your battery is not holding a sufficient charge, perform a calibration first, and then reexamine your battery's health.