I've read elsewhere on this forum that the black batteries are the older lead acid, and the white ones are the newer AGM type. My understanding is that you can replace the black ones with the same type and not have to register or reprogram, but if you replace it with the AGM type, you do. Not sure if this is correct. I wish someone would clear this up for me.

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2007 X5 4.8i Space Gray
2001 X5 3.0 Titanium Silver