In a new support document, Apple describes how to safely use the MagSafe Charger that is designed to work with iPhone 12, iPhone 12 mini, iPhone 12 Pro, iPhone 12 Pro Max, Apple MagSafe accessories, and Qi-certified devices and accessories. Don’t place credit cards, security badges, passports, or key fobs between your iPhone and MagSafe Charger or they may be damaged.
Before you place your iPhone on your MagSafe Charger, make sure that no objects (like credit cards, hotel key cards, or transit cards) or debris are between them. If your device has a metal case or if it’s very thick, remove it. Also remove iPhone Leather Wallet with MagSafe. If you have a MagSafe case, you can leave it in place.
Don’t place credit cards, security badges, passports, or key fobs between your iPhone and MagSafe Charger, because this might damage magnetic strips or RFID chips in those items. If you have a case that holds any of these sensitive items, remove them before charging or make sure that they aren’t between the back of your device and the charger.
Apple also explains that, as with other wireless chargers, your iPhone or MagSafe Charger might get slightly warmer while your iPhone charges. To extend the lifespan of your battery, if the battery gets too warm, software might limit charging above 80 percent. Your iPhone or MagSafe Charger could get warmer and charging could take longer after heavy use. Your iPhone will charge again when the temperature drops. Try moving your iPhone and charger to a cooler location.