Keep a per-device record for years, see the wear rate, and find out when a Mac battery is likely to reach 80% health, or that it's too early to say. Some of that history existed before you ever opened the app.
Once there is enough history, WhatBattery fits a trend through the Mac's recorded health and projects the window in which it may reach 80%, the point Apple uses as a service reference.
The harder part is knowing when not to answer. A battery's health reading is the fuel gauge's own estimate: it sits still for weeks, then steps when the gauge recalibrates. A few weeks of that can look like a steep decline and is not one. WhatBattery tests whether the trend is real before it will name anything, and says nothing when it is not.
Your battery's fuel gauge keeps per-cell readings, and macOS surfaces none of them. WhatBattery reads them straight out: each cell's voltage and learned capacity, how far apart they are drifting, and the extremes the pack has seen across its whole life, including before you installed anything.
Cell balance is the useful part. A pack that is genuinely failing usually shows one cell pulling away from its neighbours well before the headline health figure moves.
Dense telemetry helps explain what happened during a charge or drain. Sparse monthly health records show the slower wear story across every device.
Explore charge, temperature, voltage, and power over a selected range, with minimum, average, and maximum values. On a fresh install, the charge chart also imports days or weeks of history from macOS's own sleep and wake log, drawn as a distinct dashed line from anything WhatBattery has measured itself.
Keep one durable record per device per day, rolled into monthly health and cycle summaries for Macs, iPhones, and iPads.
Turn the current reading and lifetime summary into a one-page PDF or printout for a warranty claim, a Genius Bar visit, or a resale listing.
For deeper analysis, export recorded samples as CSV or JSON. Health history can also be backed up and restored.
History, runway, reports, and export are included in WhatBattery Pro.