When iPhone says “Slow Charger”
Recent iOS versions can show "Slow Charger" on the battery screen. 1 It indicates the iPhone thinks it is drawing less power than it could. Apple has not published the exact wattage threshold that triggers it, and we do not guess it. Work through the checklist below. If the message persists with a USB PD charger of the right rating, a known-good cable and a cool phone, try another wall socket and contact the charger's maker.
Troubleshooter: my iPhone charges slowly on 20W
- Is the phone hot to the touch, or in a hot place? → Yes: cool it, remove the case, retry. → No: go to 2.
- Is the battery already above 80%? → Yes: slower charging is normal; check Charge Limit and Optimized Battery Charging. → No: go to 3.
- iPhone 14 or earlier: are you using a USB-C to Lightning cable? → No: you need one for fast charging. → Yes, or iPhone 15 and later: go to 4.
- Does a different, known-good cable help? → Yes: replace the cable. → No: go to 5.
- Is the phone busy (game, navigation, hotspot)? → Yes: pause it and retry. → No: go to 6.
- Does a USB-C meter show about 9 V during charging? → No, 5 V only: the adapter is not negotiating USB Power Delivery; try another adapter and check the first one's authenticity and BIS registration. → Yes: go to 7.
- Still slow? Clean the port gently, try another socket, restart the iPhone. If it persists, contact Apple support for the phone or the charger's maker.