Thanks heap guys. I've tried it and it works! Damn "L" lol..

Anyway, quite suprisingly..yesterday morning, I've set the fridge (ARB 60L) cut off voltage to medium which is 11.4v, 0c on the temperature and ran it with few bottles of water inside. A short 20 minutes drive to the town in the night and switched it off before midnight. Early this morning I switched it on again and at about around noon it switched itself off which I presumed due to the Optima has reached the preset 11.4v. Later afternoon, had a half an hour drive to and around town. Just now, as I connect the Bosch charger to the main batteries, turn it on and went into the trol to have a look to the BCDC, its already at its float charge rate. Thats was quick..??