How much power will my samsung laptop use on 12v just playing pre-recorded DVDs. It is a 17" screen.?

I want to use it on a boat which has a bank of 3 not brand new leisure batteries, but has a 12v fridge, water pump, lights. Would I be safe watching the laptop for two hours one evening? On the 240v adapter it says output 19v = 4.76A (Samsung X60 plus)