Adding fuse to cig lighter

[mshirey]

I want to add an inline fuse to my cig lighter to help protect against frying my fuse box and another cig lighter harness. I'm not sure what amp fuse would be required. 15 amp seems way too low, but I'm not sure if a 20 or 25 amp is the right size. Any suggestions? Has anyone else put a fuse on this circuit? I would like to put some protection on the circuit since the recommended connection in the fuse box is to an unfused connection.

Thanks,
Mike