Apple iPhone Air will not charge or charges slowly

The checks in more detail

a USB port on a computer or a car charger of low power charges slowly, and a damaged cable charges not at all. Change one thing at a time: first the cable, then the adapter, then the wall socket. Check the lock screen for the charging symbol and Settings, Battery for the state. A message about an unsupported accessory points at the cable. Then the port and the heat. With the phone off, use a wooden or plastic toothpick to clean lint from the USB-C port, never metal. A phone that is hot from sunlight, a case or heavy use stops charging until it cools, so remove the case, put the phone on a hard surface in the shade, and wait.

Check Settings, Battery, Charging, where Optimized Battery Charging may be holding the charge at 80 percent. A restart comes next; if the screen is frozen, tap volume up, tap volume down and hold the side button until the logo shows. Update iOS, since updates fix charging bugs. Try a MagSafe charger to test wireless charging, and check that the magnet ring is centered, with a thin case. If the phone does not charge by any method, or the battery drains rapidly, check Battery Health for a low capacity; Apple Support can test the battery and the port. Back up first, and quote the serial number. The Air's slim body changes how you should treat it while it charges.

With less metal to spread the heat, it is more likely to warm up on a fast charger, in a pocket or under a pillow, and a warm phone slows or pauses charging to protect its battery, which looks like a charging fault. Charge it flat on a hard surface, take off a thick case and avoid charging while gaming or recording video. If you use a MagSafe charger, make sure the phone sits centered on it and that nothing, such as a credit card in a wallet case, sits between them, because a card can block the coil and may be damaged. A battery that drains faster than you expect, with a Battery Health figure well below a new phone's, can be replaced by Apple.