One is the same - the converter can both charge and operate the boat's systems up to 35 amps. If, for example the boat's systems demand 50 amps then both the battery and converter/charger contribute until the battery is depleted. If the boat's systems are demanding 25 amps and the battery is demanding another 30 amps in bulk charging then the converter charger will only provide bulk charging at 10 amps.On the topic of charging could someone confirm my thoughts on the following. Have just purchased a 1990 350 with a converter/charger on board. The manual says the charger puts out 35 amps for charging and the converter 20 amps for operating all 12 volt acces. Am I correct that when the converter/charger is operating all 12 volt acces are being supplied by the converter and not the battery bank? And the charger is charging the batteries with no draw down from the 12 volt acces.