Why does my Surveyor shut down when it is not in use?

FAQ - Surveyor 4a

1. Can the rechargeable battery in my Surveyor 4a power my DataSonde or MiniSonde?
2. Is the handheld waterproof?
3. What type of batteries are required?
4. Q: Why does my Surveyor shut down when it is not in use? A: The Surveyor 4a will automatically power off if it has not been used for several minutes. The user can set and change this feature.
   
   
5. How long does it take to recharge the Surveyor battery?