Oops...
Makes you wonder about the dehumidifiers people leave on their boats, too.
I have a small space heater that I bring down to the boat. Only use it while I'm on the boat; never leave it there when I'm gone and only have it plugged in when I am using it.
After my experience with the exploding shore power cable I am now even leery of leaving the battery charger on when I am not there...