Spare Key Battery

[Willy Nilly]

I don't think the spare key for my Jazz has ever been used and the buttons don't open and close the car, but the car starts so I assume the battery is flat. Does it charge up if the key is used (this may be one of the more stupid questions) or does it require a new battery?

[Lubi325]

These do have a battery within the key fob. (it is not a rechargeable one)
Depending on the year of the Jazz, it will probably be a CR1616

[cuprabob]

As said, a new battery should resolve the issue.

The reason why the key still starts the car is the immobiliser RFID chip in the key is energised by a field from the reader in the ignition switch and does not get it's power from the keyfob battery.

The battery powers the circuitry for the locking and unlocking function.

[Willy Nilly]

That you. Sure I read somewhere that some keys recharge in the ignition, but might have either dreamt it ot it's balls.