>can an open trunk drain a 2nd gen prius battery?

i just started a road trip with my prius with a bad 12v agm battery. everytime i pull it out of storage the battery is dead and sometimes it starts with jump pack and other times i have to trickle charge it back up.

well first night of road trip we sleep in front seats at a truck stop and car starts up fine next morning.
next night we sleep on floor at a beach and the car starts fine next morning
last night we slept in the back with the trunk open and this morning battery is so drained the jump pack wont start it.

wtf is going on? can an open trunk severly drain a car battery? fuck i hate car electronic systems. so glad my truck is manual everything.

new battery is like $350 though i found a wholesale-er with replacement battery for $170 but i wont be in that area for another few days