Open vehicle without key card

Hello together, I have a Megane Grandtour 1,9 dCi. To this question or problem: I am with the car of the often during camping holidays, valuables and div. other objects I then always store in the car, only by constantly opening, close with the key card it has happened several times that after 4 to 5 days (about 20 times up and to make) the battery was flat and the car has not started. Is there any trick as I get the trunk without the key card (electronics) open, or can I deactivate somehow the whole interior lighting and other things that are turned on when the card is activated? Does someone have similar experiences or a good tip as I can handle it all. Have already thought about whether one can act against the problem by various fuses, only which would be that I have to pull out?