To see the charging amps from the converter to the battery the clamp-ammeter must be placed over the "POS"(+) post cable going from the converter/charger to the battery. Used anywhere else is an exercise in futility.
Also; if you never saw at least 14.4 volts (read at the battery-terminal) you can assume you never had any bulk charging taking place.
As for the dealers installing inappropriate chargers and batteries; they also install cheap omi-directional antennas good for 10 to 20 miles. Who camps in the city? These options look good for the ill-informed.