The same circuit breaker that delivers current from the converter/charger to the battery also conducts current from the battery to the 12 volt fuse/distribution panel and most of the 12 volt DC devices. The 12 volt circuit from the converter/charger output goes from the converter/charger to the distribution/fuse panel, to the circuit breaker connected to the 12 volt buss bar, which is connected to the battery positive. If the DC converter/battery breaker trips while you are plugged in to shore power, you will never know it until you are unplugged from shore power, when the smaller 12 volt devices suddenly don't work.
The convertor/charger puts out enough current to act as a substitute "battery" to the distribution panel when the rig is plugged in to shore power. Typically, the landing gear and slides motors are directly connected to the buss bar, and will not work if the battery is drained. If the charger/battery circuit breaker is tripped, even plugging in to shore power will not energize these motors if the battery is drained.