+1 to sourcing the AGM batteries from the Dealer. In my area, the 105 Ah battery lists for ~$240 from BMW parts and that is competitively priced vs the auto parts store brands. Costco doesn't even stock the H9 battery and would have to be ordered.
You have to be careful and do your homework as many of the H9 Batteries are not rated for 105 Ah (they're 100 Ah or 95 Ah) so a guy would have to code those as well as register.
My original AGM battery is 9 years old now. State of Charge is nearly constant at 80%. That's a long time for a battery to last, imho, so that's good enough for me to stick with OE and not even bother with saving a few bucks on aftermarkets.
+1 to
Qsilver7 for all the battery replacement replies he's made. Because of him I'm a BMW Battery Dealer Believer.
