Most cameras have a built in battery. You can set a sensitivity setting so it turns on to record for 3 minutes or so. Some cameras can be set to record for a short time period after power it cut off. The only power overhead that I think would work, would be the red nose sensor. Or the internal motion sensor. The ash tray port has power all the time, I think. A camera running all night shouldn't drain a good battery. After a day or two, the battery would be too low to start up.
The glove fuse box has usable power.
After you wire in the camera, you can use a voltmeter to determine amp draw. Find the fuse and measure voltage drop across the fuse. The X5 has to be in sleep mode.