Do car clickers have batteries?

December 10, 2005 8:16 PM

Do car remote entry clickers have batteries, or are they passively activated by a field generated by the car?

The Web gives conflicting information on this question. Are the car remote entry clickers (with unlock, lock, open trunk, panic, etc., buttons) powered by batteries? Or do they have a passive RFID coil that does not require batteries in the clicker itself?

posted by qslack to travel & transportation (11 comments total)

Batteries.
posted by cushie at 8:17 PM on December 10, 2005

Mine (Lexus) has a battery. I replaced it once -- and although I don't remember the exact dollar amount, it was damn expensive.
posted by cribcage at 8:18 PM on December 10, 2005

There are remote clickers of both kinds. I know the newer BMW ones get charged via induction in the ignition.
posted by reverendX at 8:19 PM on December 10, 2005

It depends on the car. Some newer models are using RFID on the keys, and don't even require that you put the key in the ignition.

Older ones are all batteries.
posted by I Love Tacos at 8:22 PM on December 10, 2005

Ones that operate from a distance, outside the vehicle are always battery powered. RFID's range is incredibly limited and any passive induction would only work within the car. And even then, it takes roughly 7 antennas.

That is to say, even if there's a key fob you can wave around in your car to start it, if you can start it from a distance, it has batteries of its own.
posted by disillusioned at 8:31 PM on December 10, 2005

I guess I was a little confused by the question at first. There are battery powered key fobs that don't require you to ever change the battery, because the battery is constantly charged by an induction coil in the ignition.
posted by reverendX at 8:41 PM on December 10, 2005

I think there may be confusion between the key and the fob.

The fob definitely has a battery, since it operates at a distance.

My VW key has a little RFID portion as well, but that operates only when the key is in the ignition. It's part of the "engine kill" system which makes it hard to hotwire the car, I guess.
posted by MiG at 9:04 PM on December 10, 2005

Ones that operate from a distance, outside the vehicle are always battery powered. RFID's range is incredibly limited and any passive induction would only work within the car. And even then, it takes roughly 7 antennas.

Nope. There are RFID-based keyless entry systems that work from outside the car. Standard car-zappers are battery based, but there are newfangled RFID ones.
posted by I Love Tacos at 10:47 PM on December 10, 2005

Whoa -- do we have any small electrical objects which are passively activated by a field generated by some mother appliance? News to me -- I'm reminded of Tesla's dream to broadcast electric power.
posted by Rash at 11:23 AM on December 11, 2005

do we have any small electrical objects which are passively activated by a field generated by some mother appliance?

Yep. Take a look at FasTrak or E-ZPass for commonly available examples. The tags in both cases are powered by fields generated by the tag readers.
posted by I Love Tacos at 12:00 PM on December 11, 2005

My electic shaver is powered(well charged upatleast) by a field generated by its charging station.
Its so it can be used in the shower without having any thing open to the water.
posted by Iax at 3:47 PM on December 11, 2005