I can't remember the last time I disagreed with RC but this comment makes me uncomfortable. No issue as long as you are on the boat. Leaving a conventional extension cord connected when you leave is counter to ABYC recommendations and manufacturers specifications for the cord. If your marina is paying attention they'll be unhappy since it will violate the terms of their facility insurance.
If they have a properly wired marina, and the pedestal offers a GFCI protected 15A or 20A outlets, there is nothing in the ABYC or NEC that prevents an owner from plugging an extension cord directly into a battery charger that is designed for that purpose. We have hundreds of thousands of boats in the US that have only an AC battery charger but no 30A service, just a pig-tail
charger. We also have many marinas that have only 15A or 20A receptacles for catering to runabouts and lake boats.
If your marina does not offer 15A or 20A GFCI protected outlets, at the pedestal, then you do not want to do this
. You also DO NOT want to to plug your boat into a 30A NEMA L5-30 to straight blade "adapter
" that steps 30A service down to straight bladed extension cord....
A dock with 15A or 20A receptacles, if wired to code, will be protecting those outlets with 15A or 20A breakers and a GFCI outlet, much safer by comparison to a 30A adapter suicide plug.. Using a 30A NEMA L5-30 to straight bladed adapter now means your 14GA or 12GA extension cord is now protected by a 30A breaker, and this is BAD news.
Is this an "ideal" scenario
", no not at all, but there is nothing in the codes or safety standards that precludes it if the dock is correctly wired for 120V 15A or 20A outlets
. This would be considerably safer than an owner creating a dangerous on-board wiring situation, with a non-marine inverter, missing safety Earth grounding and incorrect wiring practices that could kill someone.
In a marina with only 30A or 50A service extension cords and adapters, to get to straight bladed extension cords, should be banned by the marina. The use of 30A to 15A or 20A straigth blade is what is dangerous because of incorrect OCP for teh cord being used.
Again I only recommend this for a vessel where the dock is already properly wired for 15A or 20A 120V GFCI protected outlets not when a 30A to 15A or 30a to 20A adapter