Can a Key Fob Drain a Car's Battery?

A person unlocking a car with a key fob. Photo: Kiyoshi Hijiki/Getty Images

Discovering that your car battery is dead, especially when you’re away from home, can ruin your day, leaving you stranded and in need of assistance. But is it possible that your key fob is the culprit when it comes to your dead battery?

“A key fob will constantly try to communicate with the car. And that does cause a slight drain on the battery, but generally that won’t completely drain a healthy car battery,” says Mike Monticello, Consumer Reports’ road test manager. “The key fob is, in a sense, causing the issue. More likely the car’s battery is old or aging.”

Consumer Reports has test cars that we keep in our shop all the time—sometimes even for several weeks without being driven—and we almost never have a battery draining issue. Of course, these cars all have fresh batteries. When we do have a problem, it’s usually because someone left an accessory on or the key on. 

If you think your key fob is draining your car’s battery, it’s likely time to get a new battery. Also, when you’re sitting in your car, say, waiting for someone, make sure that the ignition is turned completely off. Because if it is in accessory mode, you could be draining the battery. If the car is completely off, it should not be going dead in 30 minutes from just sitting.