Symptoms
- Battery drops from 20% to 1% suddenly
- Percentage jumps up several points without charging
- Phone shuts off while showing remaining battery
- Battery percentage behaves inconsistently
Likely causes
- CommonBattery calibration driftThe percentage estimate can drift out of sync with the actual charge over time.
- CommonAging battery with reduced capacityOlder batteries hold less charge and can report less accurately near empty.
- PossibleCold temperature affecting battery readingsBatteries can temporarily read lower in cold weather and rebound when warmed.
- PossibleSoftware bug in battery reportingAn OS bug can occasionally misreport charge level.
- Less commonDamaged batteryPhysical battery damage can cause erratic voltage and reporting.
What to do
- Let the phone fully charge to 100% uninterrupted.
- Use the phone normally until it powers off on its own from low battery.
- Charge it back to 100% again in one session without interruptions to help recalibrate.
- Check battery health under Settings for a capacity percentage; below 80% is commonly considered degraded.
- Avoid extreme temperatures, since cold and heat both distort readings.
- Update the OS in case of a known reporting bug.
- If jumps continue after recalibration, treat the battery itself as suspect.
When to call a pro
If battery health reports low capacity or the phone shuts down well before 0%, a battery replacement from a repair shop is the fix.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.