An electronic vapor provision device comprising a battery assembly 8 and a vaporizer 24, wherein the battery assembly 8 comprises a power cell 10 and a computer 12, the vaporizer 24 is releasably connectable to the battery assembly 8 and the computer 12 comprises a computer processor 16 and a memory 18; wherein the computer 12 is configured to detect whether the vaporizer 24 is connected to the battery assembly 8; the battery assembly 8 further comprises a capacitor 38; and the computer 12 is configured to first charge the capacitor 38 and then detect whether a vaporizer 24 is connected to the battery assembly 8 by measuring whether the capacitor 38 is discharged.