20–80% is the longevity zone for lithium-ion. Top-ups here are gentle on the battery.
NAXCharge is watching for a power source. Connect your charger and detection will start instantly.
Enter your device's battery Wh above (check the spec sheet or `powercfg /batteryreport`).
Plug in your original charger, keep the screen at fixed brightness, then start the timer.
Let charging stabilize past the initial surge for a reliable %/min reading.
From your charger label (e.g. 20W, 65W) or a USB-C meter. We compute an efficiency factor.