Thanks everybody! The charger actually had a green LED this morning, so it stopped charging. I had to go out, so I ran the trailer's fan while still connected to the charger, for about 2 hours. Then I turned off the charger and am running the fan a bit more, just to prove to myself that the "full" charge is more, this time. I won't let it go so low that the battery cuts off, but I'll give it an 8 hour run, as it would get while sleeping with the fan on.
I think it's all good now. Thank you, thank you, thank you!!
Deb