No, you should not mail car keys with the battery still inside. This is a significant safety hazard prohibited by major carriers like USPS, UPS, and FedEx. The small lithium coin batteries (e.g., CR2032) commonly found in key fobs are considered hazardous materials because they can short-circuit, overheat, and potentially cause a fire if they come into contact with other metal objects like keys or loose change during transit.
The safest and only fully compliant method is to remove the battery from the key fob before mailing. The key fob itself, now inert, can be shipped without restriction. The battery must be packaged and shipped separately following specific regulations for lithium cells, which often means taping the terminals and placing it in a separate plastic bag. However, for a single spare battery, it's frequently easier and cheaper to simply purchase a new battery at your destination rather than mailing the old one.
For context, here are the relevant regulations from major U.S. carriers regarding mailing loose lithium batteries, which is what a battery inside a key fob effectively becomes:
| Carrier | Policy on Mailing Lithium Batteries Installed in Devices | Policy on Mailing Loose Lithium Batteries | Key Restriction |
|---|
| USPS | Generally prohibited internationally; domestically must be installed in device and packaged to prevent activation. | Prohibited in international mail; tightly restricted in domestic mail (generally not allowed for public). | Publication 52 states batteries must be installed in the equipment they operate. |
| UPS | Permitted if installed in the device and packaged securely. | Allowed only under specific Dangerous Goods contract and packaging. | Requires proper classification, packaging, and hazard labels for loose cells. |
| FedEx | Permitted if installed in the device and packaged to prevent damage and accidental activation. | Allowed only for approved Dangerous Goods shippers with correct packaging. | Loose batteries are regulated as hazardous materials and require special handling. |
To mail your keys safely, follow these steps:
- Remove the Battery: Carefully open the key fob and take out the lithium battery.
- Package the Keys: Place the battery-less key fob and mechanical key in a padded envelope or small box.
- Handle the Battery Separately: Do not place the loose battery back with the keys. To mail it, you must declare it as hazardous material, which is complex. The most practical solution is to discard the old battery responsibly and instruct the recipient to buy a new CR2032 battery locally, which is inexpensive and widely available.
