Can this device be connected to a 12v usb input I.e Car or Caravan type A USB adapter?

The Nitecore Ci2 and Ci4 chargers comes with a USB-A to USB-C cable so they can be plugged into any standard USB-A power source that can provide enough power. 

It supports Input: 5V-2A / 9V-2A / 12V-1.5A 18W (MAX).

We would suggest 5V-2A as a minimum.