Hi there,I have only changed battery once and followed the guidelines on the forum, the majority of posters say no need to use any sort of device to maintain current and keep radio settings etc....I jusy unplugged the battery and reconncected and lost my radio settings and had the airbag warning come on dash, but turning the steering wheel full lock left and right resolved this issue.....

get the garage who swapped out battery to resolve issue, I agree must have something to do with device they used to keep power to system

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E53 X5 3.0d SUV prod.date 11/2004 eng.variant M57N Europe Right hand drive N