Is it possible to replace the battery in the key?
 

I dont know if I know how to use the search thing properly, but every combination I try with this, I just get a million hits with battery and none with key.
I know the battery charges in the ignition and I did leave it locked in the garage overnight with the key in position 1. But alas, it still doesnt work. It did work for a few months, but now the buttons dont work.
Any help appreciated.
Thanks.
Ben.

Anything is possible. It just depends on your skill set. Me I would just go and buy a new key.

https://www.youtube.com/watch?v=e1o9vH3mgmg

Others have done it here. I'm with upallnight and getting a new key though. The keys aren't really designed to come apart....

You can.. Its not that big of a deal... It does require some Xacto blade skills as you will be cutting open the key along the entire seam.. Once you get it open the battery is soldered/welded in place.. You need to cut it out...Replacements can easily be had on eBay... before you do this make sure you key doesn't need to be simply programmed to the car... My spare key hadn't worked in forever and just sat in my drawer for years... i finally decided to open it and replace what I thought was the dead battery... only to find the battery was still fine.. the key just needed to be programmed...

Good luck!

the battery is charged by the coil when car is operational, not when it is stationary. Also, do not allow the key to remain in the ignition when the car's main battery dies (like listening to radio for couple of hours) as this may de-synchronize (is there such a word??) the key from the car, and at this point the key becomes a paperweight!!!

The keys are molded shut, so when you cut it open make sure you reseal it rather well, so it does not fall apart in your pocket... How do yo know it is dead? maybe, like Rob said, it is just not programmed into the car?

I tried but couldn't get it to work. Detaching the old battery from the solder points was the main issue for me -- ended up ruining the metal part that contacts the battery.

Someone should open a business putting new batteries in old BMW keys. Big demand.

You can buy a new key cover on eBay without the inners. Then you will need to have someone cut the blank. Like I said better to just buy a new key and use the old key as a spare to open the doors manually and start the X.

I did what MRBMWX5 did too. Not hard, but its not fun putting the key back together and gluing it back together as I used a silicone to make it water proof again and at the same time tried NOT to get the black silicone everywhere. I ended up with a great/perfect result but not without my fair share of cuss words and re-do's. I wanted to make sure it fit back perfectly.

Tom = DIY Master

;) :bow: :D

Did I miss any indication that you've tried to reinitialize the key after letting it recharge overnight in the ignition?

BTW, the key does charge in the ignition in position 1-3. And if one chooses to do this...I highly recommend that you hook up a battery charger to the jump start locations in the engine bay..because if you allow the car's battery to die with the key in the ignition...there are multiple threads on multiple BMW forums where doing this has killed the key permanently...for some reason if the car battery dies with the diamond shaped key in the ignition...99% of the time the key will never start the car again for some reason. :dunno:

Here's more info about the diamond shaped keys:

I did it using Tom's DIY, for my E39 key.

If you do it properly with a soldering iron it takes no longer than 10 mins.

First remove the old solder connections with some solder wick. The battery should fall out now.

You can find the correct rechargeable battery on ebay (with correct welded legs)

Then just solder the new battery connections in place.

WOW!
Thanks guys for the overwhelming response.
I dont think it needs reprogramming, as I hit the unlock button on it yesterday and it worked. But it didnt work again.
I think Toms DIY is the answer. Thanks again.
Ben.

Ok, so I cut my key apart, (and my thumb), got the guts out of it and went out to the car and hey presto, the damn thing works everytime! put it back in the casing and no go, well worked once or twice. Take it out of the casing and it works faultlessly. Go figure?
I guess Ill change the battery as what else could I do.
Thanks again for all the help everyone.
Ben.

Well you've already cut the key open, but save yourself some trouble and send it to this guy for a proper repair. I tried to repair mine and like yours it worked for a few weeks then died, the guy in the link repaired my key for 40 or 50 bucks, well worth it. I then went ahead and bought a new key from my local dealer for $160, now I have two fully functional keys!:D I see your in the land down under, hopefully the shipping won't make it cost prohibitive.

BMW General Module 5 (GMV, ZKE V)

Did this last night as one of my key fobs wasn't working.
A $7 battery off ebay, $2 tube of epoxy and 15 mins work.

I reprogrammed it and it works 100%

What a fantastic DIY. Thanks.