Glossary · 用語
Battery vocabulary.In plain English, with sources.
Short definitions for the terms that come up when you’re trying to understand a MacBook battery: what they mean, what Apple actually says about them, and how Battery Sensei handles each one. Use the list as a reference, or read it end-to-end in fifteen minutes.
Battery health
Cycle count
One battery cycle equals one full equivalent discharge of your MacBook’s battery. Discharging from 100% to 50%, then charging back, then discharging to 50% again counts as one cycle, not two.
Battery health
Battery health is the current maximum capacity of your MacBook’s battery, expressed as a percentage of its original design capacity. A new battery starts at 100%; macOS marks it “Service Recommended” at 80%.
Design capacity
Design capacity is the original mAh (or Wh) capacity your MacBook’s battery was built to hold when new. Current capacity is measured against this baseline to produce the Battery Health percentage.
Charge cycle
A charge cycle is the full equivalent of using 100% of your battery’s capacity, in any combination. Two days at 50% drained each equals one cycle. Five days at 20% equals one cycle.
Battery calibration
Battery calibration is the process of re-aligning your MacBook’s charge gauge with the battery’s actual capacity. Modern Apple Silicon MacBooks calibrate automatically. Manual calibration is unnecessary and can shorten lifespan.
Cycle-count threshold
The cycle-count threshold is the number of charge cycles your specific MacBook is rated for before capacity is expected to fall below 80%. Modern MacBooks (Apple Silicon and 2018+ Intel) are rated for 1,000 cycles.
Charging
Optimized Battery Charging
Optimized Battery Charging (OBC) is Apple’s on-device feature that uses machine learning to delay charging your MacBook past 80% until it predicts you’ll need a full charge, usually just before you unplug.
Low Power Mode
Low Power Mode is a macOS setting that reduces processor speed, display brightness, and background activity to extend battery life. Available on MacBooks running macOS Monterey or later.
Trickle charging
Trickle charging is feeding a small continuous current to a fully charged battery to compensate for self-discharge. Modern MacBooks don’t trickle-charge. Once the cell is full, charging stops, and resumes only when capacity drops several percent.
Watts in / out
Watts in / out is the real-time rate of energy flowing into or out of your MacBook’s battery, in watts. Positive watts in = charging; positive watts out = running on battery; near-zero balance = the system is pulling exactly what the adapter provides.
Heat and throttling
In the app
Looking for something longer? Guides collects long-form posts that combine several of these terms. What a healthy cycle count looks like, whether to keep your MacBook plugged in, and how Apple’s Optimized Battery Charging actually works.