0 Replies Latest reply: Jul 14, 2009 6:35 AM by neuroanatomist
neuroanatomist Level 7 Level 7
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Apple notebook batteries – maintenance and troubleshooting

Apple notebook computers use lithium-polymer (MacBooks and MacBook Pros) or lithium-ion (PowerBooks and iBooks) batteries as a portable power source. The newest members of the MacBook Pro lineup have built-in (non-removable) batteries, which are physically larger and use a modified charging scheme for a longer lifespan – you can read more about them on this linked page. The following tips should help you get the most use out of your battery, and help with troubleshooting if you are experiencing problems. A short list of do’s and don’ts is followed by more detailed information, for those who want the details.

*Do’s & Don’ts*

DO use your battery frequently and lightly, ideally completing 1-2 charge cycles per week (minimum one charge cycle per month).

DO properly calibrate your battery when new and approximately every 2-3 months thereafter.

DON’T fully discharge your battery frequently (the infrequent, periodic calibration is an exception).

DON’T store your battery (or your computer) in a high temperature environment, such as the trunk of a car, especially a fully-charged battery.

DON’T run your MacBook or MacBook Pro on AC power with the battery removed.

*Usage Pattern*

Lithium-based batteries function best when used fairly frequently but lightly. Apple states +"An ideal use would be a commuter who uses her MacBook Pro on the train, then plugs it in at the office to charge. This keeps the battery juices flowing."+ Note that there is no "memory effect" for lithium-based batteries, unlike nickel-based batteries (NiCd, NiMH) which perform best when fully discharged then fully charged. It is best not to completely discharge your battery, with the exception of calibrating it (see below). It is also not a good idea to run on AC power all the time. Note that when you are running on AC power, there is no danger of "overcharging" your battery – the Mac will not initiate charging of the battery if the current charge is 95% or higher, as described in this kbase article. Basically, a good rule to thumb is to run on AC power much of the time, but run on battery power for a while a few times per week. Using the battery for 2 full charge cycles per week equates to 300 cycles in 3 years, which is the optimal use. An explanation of a "full charge cycle" can be found on this page. Note that for Apple portables with a removable battery, you _should not_ run a MacBook or MacBook Pro on AC power with the battery removed - Apple strongly recommends against this for two reasons: first, the risk of lost data and damage to the hard disk directory structure if the MagSafe plug is accidentally disconnected, and second, the computer will reduce the CPU processor speed. The latter is due to the fact that the CPU will sometimes (for brief periods) require more power than the AC adapter can provide, and the additional power is drawn from the battery; the OS throttles back the CPU to avoid this situation.


The battery has an integrated microchip that acts as a "fuel gauge." Calibration resets this gauge, which allows the OS to better determine times to charge and discharge the battery. Calibration should be done approximately every two months. Failure to do so for a long period of time can result in the microchip "fuel gauge" in the battery losing the ability to accurately determine the remaining charge, and it will report that there is more charge in the battery than is actually present. As a result, the computer will not initiate Safe Sleep at the proper time, and instead undergo a hard shut down, one of the main causes of hard drive directory damage. Once the battery is in the state resulting from a failure to calibrate, it is not possible to calibrate the battery, and it will need to be replaced. For Apple portables with removable batteries, note that Apple specifies, +"A _properly maintained_ Apple notebook battery is designed to retain up to 80% of its original capacity at 300 full charge and discharge cycles."+ For MacBook Pros with built-in batteries, the battery should maintain 80% of it’s original capacity for 1000 cycles. Calibration is considered part of proper maintenance.

*Battery Life and Battery Lifespan*

Battery life is how long the battery will power the computer on a full charge. To maximize battery life, consider turning down the brightness of the display, which is one of the major power consumers in a notebook computer, and if you don’t need Bluetooth and/or Airport connectivity, consider turning those off as well. Apple offers these suggestions for maximizing notebook battery life. In practice, battery life is usually somewhat less that stated in the specifications for the various Apple notebook computer models – Apple’s testing of ‘wireless productivity’ is likely limited to browsing simple websites and basic word processing. During ‘real world’ use, battery life will normally be in the range of 1-3 hours less than the specified battery life, depending on model, usage and activity. If life is shorter than expected, see the Health and Troubleshooting sections below. Battery lifespan is how many cycles/years the battery will hold sufficient charge to power the computer for a reasonable time. For Apple portables with removable batteries, a properly maintained lithium-based battery will last approximately 400-500 charge cycles or 3-4 years, +whichever comes first+. Note that this means even an unused battery loses capacity, due to the continuous nature of the chemical reaction and the buildup of oxidation in the cells. For MacBook Pros with built-in batteries, Apple’s ‘adaptive charging’ results in a significantly longer battery lifespan.

*Battery Health*

You can check the condition of your battery using System Profiler (Apple menu > About this Mac > More Info > Power section). The relevant numbers are Full Charge Capacity and Cycle Count. Mac OS 10.5 Leopard also provides a readout of battery Condition (not available in 10.4 Tiger), based on those parameters. “Health” refers to the full charge capacity of a battery relative to the nominal full charge capacity of a new battery, expressed as a percentage. Programs such iStat and CoconutBattery report the health, or you can calculate it manually: full charge capacity from System Profiler / nominal new full charge capacity * 100. For Intel-based Mac portables, nominal new full charge capacities are:

MacBook (Original, removable battery) - 5093 mAh
MacBook (Late 2008, removable battery) - 4167 mAh
13” Macbook Pro (Mid-2009, built-in battery) - 5478 mAh
15" MacBook Pro (Original, removable battery) - 5556 mAh
15" MacBook Pro (Late 2008, removable battery) - 4630 mAh
15” Macbook Pro (Mid-2009, built-in battery) - 6665 mAh
17" MacBook Pro (Original, , removable battery) - 6296 mAh
17” Macbook Pro (Mid-2009, built-in battery) - 13015 mAh

Note that health-reporting widgets (iStat Pro, CoconutBattery) use rounded values for the denominator of ‘health’. The above values are calculated from the wattage of the batteries (45 Wh to 95 Wh, see the specifications for each model, which can be found here or here) and their voltage (10.8 V for all removable batteries, 10.95 V for the 13” and 15” built-ins, and 7.3 V for the 17” built-in; those values are printed on the batteries); these capacities are nominal, and in practice new batteries will have full charge capacities that are slightly higher or lower than those values. PowerBooks and iBooks have batteries ranging from 45 Wh to 61 Wh - specs for individual models can be found here or here); these Li-ion batteries are all 10.8 V, so nominal new full charge capacity can be calculated by multiplying battery Wh x 92.6. (For the curious or algebraically-inclined, 92.6=1000/10.8, which converts Wh to mWh and divides by voltage to yield mAh, based on I=P/V derived from Ohm’s law). When Apple specifies, +"A properly maintained Apple notebook battery is designed to retain up to 80% of its original capacity at 300 full charge and discharge cycles,"+ they are referring to 80% health. Please note that health fluctuates from cycle to cycle, depending on factors such as the pattern of charging within recent cycles, ambient temperatures during use, and time since last calibration. It is normal for health to move up and down within a range of ~10% (e.g. between 86% and 96% over time).

*Troubleshooting – short battery life and sudden shutdowns*

If battery life is unacceptably short, it may be due to a background process that is running a high percentage of CPU activity. Check Utilities > Activity Monitor > CPU tab, set the pop-up menu to Active Processes, click on the CPU column to sort, and see if anything is using a high amount of CPU capacity. Short life and sudden shutdowns may also be due to a defective or an old battery - check the battery health and cycle count. If the cycle count is in the 400-500 range (or higher) for removable batteries, the battery has exceeded its useful life, and needs to be replaced. This does not indicate a defective battery - batteries are considered a consumable part, and need to be replaced at the end of their useful life. If the cycle count is less than 300, and the health is less than 80%, the battery may be defective - this applies primarily to the newer, Intel-based Mac portables. For a certain period of time (a rather long period, in fact), Sony produced defective batteries (both Li-polymer and Li-ion) - this issue affected many laptops (Apple, Toshiba, Dell, etc.) that use batteries manufactured by Sony. Apple officially acknowledged these defects for Intel-based notebook computers, as stated on this page, and extended the battery warranty to two years from date purchase for all Core Duo machines bought between February 2006 and April 2007. Battery Update 1.2 was designed to test batteries and expose defects. Note that there were actually two battery replacement programs from Apple concerning Intel-based Macs – both programs are _now officially closed_. One was an exchange/recall for specific serial numbers, and applied only to a relatively small number of 15” MacBook Pros; the other was the more general replacement program for the defective Sony batteries. There was also an exchange/recall for battteries in the 12" iBook G4 and 12"/15" PowerBook G4, also due to manufacturing problems at Sony (these were the batteries with a safety risk).

Following the above steps should ensure a long and useful life for the battery in your Apple notebook computer. Hope this helps...

This is the 2nd version of this tip. It was submitted on July 13, 2009 by neuroanatomist.

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