5 series touring - second battery?

[alastairwatt]

thanks for the help and link to the realoem pages, so bmw did give it as option, a split charge relay and leisure battery would work out far cheaper to purchase than the bm wiring kit and small battery thats located behind the boot panel.

thanks, its good to know the germans think of everything!, would this second battery just be to run the odd 12v item or has it a purpose?

[Paul in NZ]

dont know why it was installed on mine.It is a 25 AH battery,about the size of a large motorcycle battery.