There's no battery in this router. So without an external power supply it won't work and will switch off straight away.

You'd have to describe how you plan to use it on a bus, coach, camper van, lorry, boat, etc? And how you plan to power it.

Teltonika offers this battery for continuous operation Teltonika Uninterruptible Power Supply

They also have a cigarette lighter connection, but there's nothing to stop it being connected to a 12 or 24V vehicle battery in another way.

It depends on what you connect it to. As a rule, it stays on because it is supposed to do its job on the CP. I have connected a radio transmitter to switch it "dead" in between so that this doesn't happen when it's not in use for long periods.

It depends on how you connect the device.
The router itself has no battery protection.