From what I've read and heard from my dealer, the keys are coded to your VIN. The master key battery is not replacable and the master keys are recharged in the ignition while you drive. So you ought to use both keys regularly if you want to set the alarm and locks. Otherwise it becomes just a lock & ignition key. I also heard that dropping them may also lead to a bad battery.

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Mark _______________________________
2001 X5 4.4i topaz blue/sand Sport, complete Dinan S2 , hitch, V1, tint, BSW Stage 1, Alpine INA-W910BT
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