Can you change the battrie in bmw key 200...

you can actually reprogramme them yourself,

what you need to do is:
1 sit inside your car with all doors and windows up
2 turn the key to ignition point before the engine turns over, take it back out
3hold the unlock button and press the unlock button 3 times whilst still holding the unlock button,
4 release all the buttons and if its worked the locks should bounce,

this is what bmw tend to try first so you are better off trying this rather then paying the hefty sum of money to them,
if you are going to do this you will need all the fob keys as when you reprogramme the one the other key unprogrammes itself,

word of advise keep swapping between your spare and usuall key to keep the charge in both keys,

hope this helps cheers

THE BATTERY INSIDE THE KEY RECHARGES ITSELF EACH TIME YOU DRIVE THE CAR, IF IT STOPPED WORKING YOU WILL NEED TO GO TO THE DEALER AND GET A NEW KEY PROGRAMED COTS ABOUT $160.00