Upgrading our power converter/inverter

I ONLY RECENTLY DISCOVERED WHERE THE ONBOARD BATTERY WAS. EVERY TIME WE UNPLUGGED FROM SHORE POWER AND STARTED OUR TREK ABROAD, THE FRIG WOULDN'T AUTO SWITCH TO GAS. THE BATTERY WAS TUCKED UP UNDER THE DRIVERS SIDE, BOLTED IN PLACE WITH NO EASY ACCESS TO CHECK WATER OR HOOK A BATTERY TENDER TO SO IT WAS DEAD. I REPLACED THAT AND I'M ADDING A TENDER FOR TIMES WE'RE NOT PLUGGED IN TO SHORE POWER AND OVER THE WINTER. THE INVERTER/CONVERTER PANEL MAKES SENSE TO ME AND I UNDERSTAND THE DIFFERENCE BETWEEN THEM I JUST WASN'T SURE I COULD REPLACE ONE WITHOUT THE OTHER OR IF I HAD TO REPLACE THE WHOLE POWER DISTRIBUTION PANEL. I COULD USE A FEW MORE AMPS OF POWER SOMETIMES.