2006 BMW 330xi whose car-keys (the automatic one) is dead. I think its batteries are dead. What are my options?
I tried driving around to charge it but that didn't work.
You should be able to get the battery changed, either by an automotive locksmith or by your nearest BMW dealer. The batteries are usually standard coin cells, but I wouldn't try changing one without checking first as you might find it will need to be re-programmed afterwards.
Try a locksmith first as they will probably be a lot cheaper than BMW!
Not sure on your 330, but on my E39 the the battery in the key is automatically recharged when it is in the ignition. There's a clever induction system that keeps the battery charged.
Your battery may not work that way and may have died.
You may also have somehow gotten the car security system to "forget" your keys, so it isn't responding to them any longer. Some BMWs have a process where you can re-learn your keys without needing to take it to the $tealer.
I know this is an old thread, but I am disheartened by the inaccuracy of the replies. Your "key" which is really a fob, runs on a coin shaped battery, namely, a CR2032. They can be purchased most anywhere (picked my two-pack at W-Mart).
Google replacement of the battery for this fob and you will find more than adequate info on how to proceed - it is really very simple.
Good luck (you've probably solved your problem by now, but perhaps others can benefit - I know I did from other similar threads).