CTEK Cig-Plug (Part No. 56-263) enables charging the battery through the cigarette outlet (if outlet is live with ignition switch off)
It eliminates any hassle, simply charge from within the car, suits perfect for CTEK's battery charger with Comfort Connect, UC 800, US 800, MULTI US 3300, MULTI US 7002, US 0.8, and MUS 4.3.
Note that the vehicle needs to have power on the cigarette outlet when not in use.
CTEK Cig-Plug fits both 12 millimeter (small Euro/BMW/Powerlet) and 21 millimeter full size automotive outlets and has a maze-like strain relief for the user's safety.