Battery charger installed. Fly lead hard wired as per Merc instructions for charging the consumer battery.
Only gripe is the length of the cables... The connection to the charger is relatively short so have had to place the charger in front of the radiator, bonnet still latches, and the mains plug is just inside the garage door.
Seems to be charging ok, and the car isn't complaining so that's something. Can just about see the display through the grill.