The converter has a max power and that's it. It does not "overload".
Within that max power, you get its rated amps at the spec voltage which in the PD's case is 13.6 volts. It will have some extra power so you will get more at the start, but the PD has some circuitry thing where it can't quite hold 45 amps at 14.4 volts so it tapers the amps a bit at the start in 14.4v mode. some other converters and chargers can hold their rated amps steady "constant current" until the battery reaches the set absorption voltage. then amps will taper once voltage is held constant in that stage.
The exact way it all happens for different chargers is called their "charging profiles" and those vary among brands somewhat.
The PD and the other brand converters will do a little more amps than the "name" size. Eg my 7355 will do 56 amps, my old Paramode 55 did 60, and my PowerMax 100 does 103 given low resistance paths to the battery.
So don't worry how many batteries you are trying to charge. As was noted earlier in the thread, it will do 45ish amps max no matter how big the battery bank is.
EDIT--RJ, the 60 amp load will be on the battery not the 45 amp converter, so all that happens is your battery will get 45 amps in while that 60 amp load is running for a net loss of 15 amps. Nothing will break.
