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Discussion Starter #1
Hi fellas,
Brand new to the forum and a bit of a newb when it comes to cars in general.
But in here to learn so I can become more savy with my car and save myself some money too!
The question I want to ask is, when I replace the battery in the key fob, do I need to worry about reprogramming it, once I’ve soldered in the new battery? Or am I safe to just replace the battery and then it’ll open and close with no problem?
Thanks
 

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2004 BMW 330 M Package 306km
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75 Posts
I’m pretty sure it doesn’t work like that. When I replaced mine I bought a whole new key I don’t believe you can just get the battery. I had two options either the entire key for a few hundred or just a valet key for under a hundred. Good luck.
 

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Here to serve y’all
2004 330Ci 85k miles
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12,407 Posts
You can replace the key fob battery, but it is rarely necessary. It’s only used for locking/unlocking (not for starting) and gets charged up while you drive. The key often gets ruined when you try to replace the battery anyway.

To answer your original question though, you should re-synch all your fobs following this guide.
 

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10,449 Posts
The fob’s battery is for the remote lock/unlock function only. The anti-theft circuit is powered by the ring antenna that surrounds the ignition lock.
 

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E46 '04 330Ci convertible 740K km
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589 Posts
It is rechargable battery, it gets recharged every time you put key in ignition. One of my keys wasn't in use at all for 13 years and yet hold charge. Another one I accidentally washed with cloth, had to cut plastic body in order to clean and dry it; it started workng again next day. I doubt you really have battery problem.
 

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IIRC it’s not a rechargeable battery. I thought it was and then was informed (by Scott?) that it is not rechargeable.
 

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E46 '04 330Ci convertible 740K km
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589 Posts
IIRC it’s not a rechargeable battery. I thought it was and then was informed (by Scott?) that it is not rechargeable.
Then we probably talk about different keys - are there they for e46? Diamond key has rechargeable battery which is pretty much everlasting. Key body is sealed and battery is soldered to plate so clearly not meant to be serviced.
 

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IIRC it’s not a rechargeable battery. I thought it was and then was informed (by Scott?) that it is not rechargeable.
What! I never said it wasn’t a rechargeable battery. It absolutely is. That is the for the diamond shaped remotes that came with E46 after early 2000 (and E39s starting the 1999). The earlier rubber button remotes with the red light that comes with E46 through early 2000 had a non-rechargeable, user replaceable CR2016 battery. My car came with the rubber button remote since it got my car new in April of 1999.

I do repair of genuine diamond remotes starting at $50. I can also make keys that work in the locks and start the engine (using chinese diamond keys cases and remotes which do not recharge in the ignition and their batteries need to replaced every 2-3 years) for <$100 so if you in the Los Angeles area let me know. For new keys I need the EWS module so if you are able to be without your car for a few days you can send in your EWS.
 
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