Yes there is a cooling fan on the converter that kicks on when the unit gets hot.
Not much info here to go on but I would have to ask have you charged your 2 month old batteries since you got them. If you purchased new battery's, installed them on the trailer and walked away from the trailer for 2 months then the battery's are probably low and may have a bad cell or two. If the battery's have been used and maintained then its probably not them.
Get out your volt meter and see were the battery's read, what is the voltage when plugged into shore power or generator? This would tell you if the converter is doing anything.