Electronic vapor provision device

1. An electronic vapor provision device comprising:

a battery assembly; and

a vaporizer,

wherein the battery assembly comprises a power cell and a computer, the vaporizer is releasably-attachable to the battery assembly and the computer comprises a computer processor, a memory and an input-output means, and wherein the computer is configured to determine when the vaporizer is attached to the battery assembly and, when the computer determines the vaporizer is attached to the battery assembly, the computer is configured in use to remain in a normal operation mode and to enter a sleep mode when the device is inactive for a predetermined inactive time, and when the computer determines the vaporizer is not attached to the battery assembly the computer is configured in use to enter the sleep mode, and

wherein the computer is configured to periodically check whether the vaporizer is connected to the battery assembly during both the normal operation mode and the sleep mode.

2. The electronic vapor provision device of claim 1 , wherein the electronic vapor provision device is an electronic cigarette.

3. The electronic vapor provision device of claim 1 , wherein the sleep mode is a low power mode.

4. The electronic vapor provision device of claim 1 , wherein the sleep mode is the lowest non-zero power mode of the device.

5. The electronic vapor provision device of claim 1 , wherein the electronic vapor provision device uses less power in sleep mode than in usable mode.

6. The electronic vapor provision device of claim 1 , wherein the electronic vapor provision device is inactive when not being used as a vapor provision device by a user.

7. The electronic vapor provision device of claim 1 , wherein:

the body comprises first and second body connection terminals, and the vaporizer comprises first and second vaporizer connection terminals; and

the device is configured such that when the vaporizer is connected to the body, the first body connection terminal is connected to the first vaporizer connection terminal and the second body connection terminal is connected to the second vaporizer connection terminal.

8. The electronic vapor provision device of claim 1 , wherein:

the body further comprises a capacitor; and

the processor is configured to first charge the capacitor and then detect whether the vaporizer is connected to the body by determining whether the capacitor is discharged.

9. The electronic vapor provision device of claim 8 , wherein the capacitor is connected in parallel with the first and second body connection terminals.

10. The electronic vapor provision device of claim 8 , wherein the computer is configured to send out a pulse and the capacitor is charged for a period of time equal to the width of the pulse.

11. The electronic vapor provision device of claim 10 , wherein the pulse is a square wave.

12. The electronic vapor provision device of claim 1 , wherein the vaporizer further comprises a mesh wick.

13. An electronic vapor provision device body, comprising:

a power cell and a processor, and configured to be releasably connectable to a vaporizer,

wherein the processor is configured to determine when the vaporizer is attached to the vapor provision device body and, wherein the processor is configured to remain in a normal operation mode when it is determined the vaporizer is attached to the vapor provision device body, to enter a sleep mode when the processor determines the vaporizer is connected to the body and the device is inactive for a predetermined inactive time, and to enter the sleep mode when it is determined, in use, the vaporizer is not attached to the vapor provision device body, and

wherein the processor is configured to periodically check whether the vaporizer is connected to the vapor provision device body during both the normal operation mode and the sleep mode.