ReviByte Tools
Battery Health & Charging Time Estimator
Physics-based estimates for charge time and battery wear. Everything runs on your device — nothing is uploaded anywhere.
Charging Time
3.85V is typical for phones — check your device spec if known.
Battery Health
Found in Settings → Battery on most Android/iOS devices, or a battery-info app.
How to use
- Charging Time: Enter your phone's battery capacity (search "[your phone model] battery mAh"), your current charge % from your battery indicator, your charger's wattage (printed on the brick), and leave voltage at 3.85V unless you know your device's exact spec.
- Battery Health: Enter the original design capacity (same spec as above) and your current max capacity. On iPhone this is under Settings → Battery → Battery Health. On Android it's usually Settings → Battery → Battery Health, though some brands hide it — a free app like AccuBattery can surface it if so.
How this works
Lithium-ion batteries charge in two phases: constant current (CC), where the charger delivers steady power up to roughly 80%, then constant voltage (CV), where current tapers off to protect the cell as it approaches full. That's the physics behind why the last 20% always charges slower than the first 80%.
Battery health is degradation of maximum charge capacity over charge cycles — most phone-grade Li-ion cells are rated for roughly 80% of original capacity after around 500 full charge cycles, though this varies by chemistry, temperature exposure, and charge habits.
These are physics-based estimates, not manufacturer-calibrated readings — actual charge controllers vary by device.