Placing RFID key cards, key fobs, or access cards on a wireless charging pad can have several important implications — electrical, magnetic, and functional.
Magnetic & Inductive Interference
Wireless chargers use inductive coupling — a magnetic field oscillating at high frequency to transfer energy.
RFID and NFC cards/fobs also use inductive coupling, but at different frequencies (usually 13.56 MHz for NFC/RFID).
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When placed on a wireless charger (which operates around 100–200 kHz for Qi), these devices can:
Experience induced currents in their antennas.
Cause magnetic interference that might heat metal components or damage the chip.
Prevent proper charging of your phone or device due to interference or foreign object detection (Qi chargers detect metal to avoid overheating).
Implication: The key card/fob might heat up, demagnetize, or fail — even if no immediate damage is visible.
Thermal Risks
Metal coils inside key fobs and cards can absorb energy from the charger’s field.
This can lead to localized heating — potentially enough to warp plastic, damage the embedded chip, or weaken adhesives.
The charger itself might shut down due to over-temperature or foreign-object detection.
Data & Functionality Risks
RFID or NFC data stored on the card/fob could become corrupted if the chip experiences voltage spikes.
Even passive tags (no battery) can have their internal circuits damaged or degraded by induced voltage.
Practical Consequences
Scenario |
Likely Outcome |
| Key card/FOB left on charging pad during charging | Possible chip failure, demagnetization, or heating |
| Metal-containing fob (e.g., car key) | Can cause charger to stop charging, overheat, or even damage charger coil |
| Thick case with NFC card behind phone | Can interfere with both charging and NFC/RFID (Apple/Samsung, etc.) |
Best Practices
Avoid placing RFID cards, fobs, or metal objects on charging pads.
If you use a phone wallet case, remove cards while charging wirelessly.
Manufacturer warnings — Extreme caution against placing cards or keys on pads.