Does Leaving A Key Fob Too Close To A Car Drain The Battery?

Key fobs have been around for a hot minute now. In fact, the AMC/Renault Alliance from 1983 was one of the first vehicles to feature a factory-installed mechanism that allowed drivers to lock/unlock doors remotely. Of course, it didn't take long for the auto industry to follow suit. By the early 1990s, remote keyless entry — the term used before "fob" became associated with the device – was all the rage.

Technology has since taken those very rudimentary fobs and bedazzled them with an assortment of functions. Now decades removed from the origin of said revolutionary convenience, you'd think we'd have figured out how to keep those now ubiquitous fobs from draining the car's battery. That's not the case, however, as they're still leeching power from your car's primary power source.

In the early days, fobs did nothing more than pop the locks, but they do much more now. Packed with circuit boards, radio transmitters, and control chips, they're more akin to miniature command centers that can do everything from remotely start the car to fold your mirrors and even summon your vehicle. And therein lies the problem. To communicate and work properly, fobs need to be within range of the car. However, if it's sitting too close, it will continue to do its job, which unfortunately can take a toll on your car's battery.

Even though fobs are constantly trying to communicate and will cause some drain, it shouldn't have much impact on a new, healthy car battery. An old battery, though? That's a different story, and it's become the root of great frustration for many — not to mention the secondary drain to the bank account that could occur if you have to replace it.

It is generally not a good practice to leave the fob inside your vehicle for this reason. Putting it completely outside of the range of the sophisticated internal radio technology it's using may be easier said than done considering a fob can work up to 100 feet away in unobstructed conditions. Thankfully, you don't need to store it that far away. In general, keeping it 15 to 20 feet away from the car is all that's needed to sever the communication loop.

Since the key fob constantly pings the vehicle, it can not only drain the car's battery, but also the one inside the fob itself. Some car brands even allow you to put that smart fob into "Power Saving Mode" to prevent this. Fortunately, replacing the battery in your fob is easy (and far less expensive) than replacing your car's battery. Still, it's a good idea to have an extra one on hand at all times.