Symptoms
- Phone charges normally when fully powered off
- Charging stalls or fails once the phone is turned back on
- Battery percentage barely rises while the phone is in use, even plugged in
- Phone shows charging icon but percentage doesn't climb while on
Likely causes
- CommonAged battery unable to both power the phone and accept a charge simultaneouslyA weakened battery's internal resistance can make it draw more power running the phone than the charger supplies.
- PossibleA background process consuming more power than the charger deliversHeavy app or screen use while charging can outpace a low-wattage charger.
- PossibleA failing charging IC or battery connectorA hardware fault can specifically affect charging under load.
- PossibleAn underpowered charger that can only just charge the phone at restSome basic chargers barely keep up even with the screen off.
What to do
- Test with the phone fully off, plugged into a known wall charger, and confirm it charges normally that way.
- Turn the phone on while still plugged in and watch whether the percentage stalls or drops.
- Try a higher-wattage adapter, like 20W or more, to rule out an underpowered charger.
- Close demanding apps and turn the screen brightness down while testing charging with the phone on.
- Check Battery Health for a low maximum capacity percentage, which often correlates with this symptom.
- Note how long the phone needs to be off before it can charge and be used again without the issue.
- If a strong charger still can't keep up with the phone powered on, the battery is the most likely cause.
- Avoid relying on 'off-only' charging long-term, since it signals the battery is close to end of life.
When to call a pro
This pattern is a strong sign of a worn-out battery; a replacement at Apple or an authorized repair shop typically resolves it completely.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.