sorry forgot to say, it has a battery pack that clips on to the dvd player, so would i just plug the car lighter adaptor straight into the dvd player and not the battery pack?
If its like my portable dvd player, I plug it into the battery, whilst on the bottom of the dvd player, therefore it will charge the battery whilst you can still use the dvd player.
Ideally, for the first couple of charges i would let the battery run down to empty and then charge it up