changing battery in key

[Kibokojoe]

My sister in law has a 2000 528i and the battery is dead in the key. Can and how do you replace it? I have studied it for a while and it doesn't look like you can open it

[Dash01]

She might want to consider putting an LED into that key, if it already hasn't got one. Uses much less juice and/or smaller battery, so has much longer life.

[Dash01]

Oh, and another thing worth considering: I read or heard somewhere (youtube, perhaps) that some batteries are actually a stack of smaller button batteries, wrapped in a roll, and that you can save a lot of money by opening the roll and removing the button batteries. If so, this would be a very cheap source of button batteries for an LED key light.

[shogun]

check here under
Car and Key Memory Programming/Coding Explanations, Nov 2004 (PDF)
Car and Key Memory Settings E38 E39 E46 E52 E53, Nov 2004 (PDF)
http://www.e38.org/

[eaglecomm]

Which key is it? The diamond style or the 3 button? If it is the diamond oem style, you have to cut around the middle with a small cutter or knife. There are pics of one being cut open on bimmerboard. Will see if I can find it. Was shown by farnarkler. The diamond keys have a battery soldered to the board. You can get a new battery that has similar solder points and solder a new rechargeable battery in it. If its the 3 button, there should be 2 screws on the back and then the key separates. Its just a regular battery you can replace.

[Kibokojoe]

Yes I have seen these pdf's. Good stuff. The problem I have is we only have one programmable key and to properly perform the syncing you have to have two programmable keys. With only one key and changing out the battery you are taking the chance of loosing its brains. What a pain in the back side. Also I have the later key, the one they call the diamond key. The earlier model appears to be more forgiving when it comes to changing the battery and programming. Who was the egg head who designed a key with a battery that is not serviceable. He should be horse whipped. With the diamond key you have to surgically remove the battery from a sealed plastic case then you have to unsolder it. You only have about 60 seconds and then it has lost its memory. Everyone who has played around with battery removal and re syncing has always had one good key so they could Frankenstein the second. A seconds key appears to be over $250 USD that is ridiculous by anyones standards.