Dad;

You must not have read my post about my first electrical fire.

Absolutely use a fuse!! My cheap aftermarket lighter/power plug shorted out and smoked the power wire. I'll be installing a battery quick connect switch and fuse when I put another one in. I had to jump out and disconnect the battery when it went up in smoke.

I think the original lighter used a 20 amp fuse. For just a GPS and or phone a 5-7 amp should be good.

Thanks

Larry