Mac notebooks: Battery terminology and key concepts
Learn more about the concepts and terms related to the removable and non-removable batteries used with Mac notebook computers.
- Consumable: Consumable parts are those that deplete over time as their internal components are used. Batteries, due to their chemical components, are considered consumables, and over time they lose their ability to hold a charge. This is normal given the nature of a consumable part. Consequently, batteries are not eligible for warranty replacement if their loss of ability to hold a charge is not due to any defect in the part.
- Cycle Count: This number represents the sum of total and partial discharge cycles throughout the life of the battery. Discharging a battery to 50% capacity twice counts as one discharge cycle and thus adds one to the cycle count.
Note: For more information about cycle count, refer to Apple - Batteries.
- Full Charge Capacity (FCC): Also referred to as simply "capacity", this refers to the amount of power as measured in mAh (milliampere-hours) the battery is capable of containing. This number lowers as the battery becomes depleted with usage and age.
- Remaining Charge Capacity: This number is represents the current amount of power left in the battery as measured in mAh and thus should always be lower than the FCC. Using the computer when not connected to AC power will cause this number to lower as power is depleted from the battery.
- Depletion: Batteries deplete over time. The amount of usable charge (or energy) that can be obtained from a battery is continually reduced as the battery is used (charged and discharged). Battery depletion over time and with usage is normal and is not considered a defect, and it is not covered under Apple's one-year limited warranty or extended service contracts. A properly maintained Mac notebook computer battery is designed to retain at least 80% of its original Full Charge Capacity for 300, 500, or 1000 discharge cycles (the number of cycles will vary depending on the computer model). After 300, 500, or 1000 discharge cycles, a battery is considered depleted and battery performance is no longer a reliable indicator of a defect.
- Runtime: The length of time a battery will power a computer. The runtime is affected by the FCC and CC of a battery as well as the load put on the system the battery is powering.
- Load: Battery runtime depends on the amount of power being consumed. Certain power-intensive processes place a heavier load on the battery and result in a much-reduced runtime per charge. The following are examples of settings or processes that can affect battery performance:
- Setting the screen to full brightness.
- Playing a DVD movie, which may reduce a battery's effective charge.
- Using disk-intensive applications, such as high-end graphics software.
- Using AirPort networking products.
- Attaching peripherals that rely on the system bus for power.
- Runaway processes.
- Sleep drain: You may notice the battery in your Mac notebook may drain up to 1% per hour (24% per day) while the computer is in sleep mode. This is normal behavior.
- Defective: Batteries that are defective (stop working due to a defect in materials or workmanship, or due to a manufacturing defect) are covered under Apple's one-year limited warranty and extended-service contracts.
- Calibrating/Calibration. The lithium ion batteries in iBook or PowerBook computers, as well as the lithium polymer batteries in MacBook and MacBook Pro computers, have an internal microprocessor that provides an estimate of the amount of energy in the battery during charging and discharging. To get the longest running time from a Mac notebook computer with a removable battery—such as an iBook or non-unibody MacBook Pro lithium ion battery—you should calibrate the battery during the first week of ownership and repeat the process occasionally to keep the battery functioning at its fullest capacity. Mac notebook computers with non-removable batteries like the MacBook Air do not require regular calibration.
Helpful battery articles:
- Tips for maximizing your battery charge
- About battery storage life
- Calibrating your computer's battery for best performance
- Optimizing energy settings for notebook computers
- Apple - Batteries
- Replacing the battery in MacBook Air, MacBook (13-inch, Late 2009), MacBook Pro (Early 2009), and later
- MacBook: How to remove or install the battery
- MacBook Pro: How to remove or install the battery