Battery supplies RV DC System when NOT connected to AC Power Source
AC Power Source supplies AC to Converter which then supplies RV DC System and maintain/charge battery
Battery POS Cable In-line fuse blown would only prevent battery from supply DC
Converter Reverse Polarity Fuses blown will prevent converter from supplying DC/charging battery (can be on backside of converter or installed on DC Dist Fuse Panel
If you have an INverter.....battery would be source of DC so battery POS cable in-line fuse (Or DC Circuit Breaker) would be suspect
More details would be helpful.....
Year/Brand/Model of RV
Brand/Model of Converter ----or Inverter if you have that instead of converter
CONverter...AC Voltage IN and DC Voltage OUT
INverter....DC Voltage IN and AC Voltage OUT