Satnav charger cable - Fused?

I have a Road Angel and a satnav, both of which came with charger cables that plug into the cigarette lighter. I had both of them hard wired in, but they were done by different installers.

The guy who did the RA cut the cigar lighter plug off & connected the bare live and earth wires with an in-line fuse. The guy who did the satnav left the plug in place, connected new wiring to the end of it and taped it all up.

The satnav has just stopped charging, and I can't figure out why. I can't find an in-line fuse anywhere in its circuit. So my question is: Does the cigarette lighter plug have its own fuse built in?

Ok, have had the car inspected by someone who knows what he's doing:

Firstly, the plug on the satnav cable was left in place for a reason. It's not just a connector, it contains a mini circuit board with a voltage regulator.

Secondly, the reason it's not charging is that the mini circuit board is fcuked and can't be repaired. New cable ordered from Ebay for £6.

Thirdly, the satnav cabled is fused, through the same fuse as the Road Angel cable. It also uses the same earth, which is handy to know for the future.