Represented by part number 2 in the second diagram.
BMW Motorcycle Battery Charger Conditioner Comfort Indicator With Eyelet 2289103
Genuine BMW Car & Motorcycle Battery Charger AGM, Lead Acid, Lithium 61432408593
GENUINE BMW MOTORRAD BATTERY CHARGER PLUS P/N 77025B5B632
Ultimate Speed Car & Motorcycle Battery Charger 6V / 12V Smart Trickle Charger
HTRC 16A Car Battery Charger 6V/12V/24V, Trickle Charger LiFePO4 Battery Charger with 10-Stage LCD & Pulse Repair, Motorcycle Battery Charger for Lead-Acid/LiFePO4
