plus 1 ^^^
Hi
if urs is stop start u will indeed have a second battery , think the main battery is under ur spare wheel and the stop/ start battery is behind the RH boot panel , , indeed the BCM will need resetting with diagnostics
batteries even new ones will require charging before hand
am wondering if the beeping sound is where systems need to be reset after battery disconnection, ie, boot / rear parking sensors, rear camera
when u hear the beep can u see any lights flashing on the dash plse , do u have multiple keys , ie , memory settings , or something on the passenger seat as there’s an occupancy sensor in the seat base
as a side note when a battery starts to get low the vehicle will start shutting down systems to preserve power , hopefully charging one/two batteries will resolve the issue
hope that also helps and plse let us know how u get on
