Apple warns that the MagSafe can generate excess heat. As a failsafe, iOS will limit charging to 80 percent if the phone gets too warm (this works for any charger). It says that this will “extend the lifespan of your battery,” but comes at the cost of longer charge times. Apple says you can avoid this by moving your phone to a cooler location if it gets too warm.
The support document also cautions that the MagSafe charger can damage the magnetic strip or RFID chip in your credit cards if they get caught between the iPhone and the charger. This foible is particularly concerning since Apple sells MagSafe wallets that attach to the back of the iPhone 12.
“If you keep your iPhone in a leather case while charging with your MagSafe Charger, the case might show circular imprints from the contact.” —Apple Support
“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 advises customers.
Additionally, users should note that the charger may leave a circular ring on cases if they are left on while charging. Apple only cautions users with leather cases, but MacRumors reports that one of its readers posted pictures to the forum showing what the MagSafe did to his plastic case (above).
None of these things are particularly hazardous but can certainly be annoying for a phone that costs so much. Removing your case every time you have to juice up will quickly get old. In hindsight, perhaps the MagSafe feature was not the best idea for the iPhone 12. Maybe Apple should have stuck with the AirPower Qi charging dock after all.