I've found that it only takes a couple of hours to charge the battery. Sounds like something else might not be working correctly. First get the battery checked, after that, it could be the convertor.
OTOH, don't worry what happens, just make sure you watch your battery meter, if it drops too low, just plug it into the tow vehicle (running of course) that will charge it also.
20XX 3/4 something TBD
2010 K-Z Spree 318BHS LX