The fuses are on the 12 volt side on the campers
converter. The converter converts the alternating current (AC) from shore power or generator to direct current (DC) from the campers low voltage systems.
My guess would be a power drop from your generator. If the problem doesn't occur on shore power then the gen set may be dropping off quickly when it's switched over. A drop in AC voltage to the converter will equal a drop in DC voltage of it's output. The lower output will then cause a quick momentary rise in amp draw to any connected device. That quick rise in amp draw can cause the fuse to blow. If the battery is waiting for a charge then it would be the hungriest and it make sense that it's the first to blow.
Visit your local rental center and rent a small inverter type generator for a day and perform a DIY test.
Alan
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