Change the battery on my old key.

[JonK]

Originally Posted by WolfX5

Logic check guys...OF COURSE there's a battery inside the key . Any radio transmitter needs a power source, even the weak 315mhz transmitters inside a BMW key fob (not that you'd want to destroy your $150.00 key just to get to it mind you, but yes - there IS a little battery inside in case you were wondering). A capacitor is not a subsitute for a constant power source, and would simply not have the reserve capacity to repeatedly transmit without being recharged after each use. Try locking/unlocking your doors a dozen or so times and you'll see what I'm talking about...

Now I am very tempted to crack my key open. Perhaps I am killing a goose laying golden eggs?
If you mean battery as something separtely replacable, perhaps not, like old remote. They're many chips out there not requiring those, i.e. My HOA fobs...
Mobil express fob, I don't know the exact name, some smart cards. They don't need batteries... If anyone know the details let me know. I am curious to know.

[SuaveX5]

Originally Posted by JonK

Now I am very tempted to crack my key open. Perhaps I am killing a goose laying golden eggs?
If you mean battery as something separtely replacable, perhaps not, like old remote. They're many chips out there not requiring those, i.e. My HOA fobs...
Mobil express fob, I don't know the exact name, some smart cards. They don't need batteries... If anyone know the details let me know. I am curious to know.

The smart card uses a serial interface and receives its power from external sources like a card reader.

[rayxi]

Originally Posted by JonK

They're many chips out there not requiring those, i.e. My HOA fobs...
Mobil express fob, I don't know the exact name, some smart cards. They don't need batteries... If anyone know the details let me know. I am curious to know.

Are you talking about the pay at the pump gas tags? Those are passive RFID tags. They use the RF signal from the pump to power it's own circuits and sends back a reply. This is not how our keys work.