There is no issue switching batteries with overlapping on states. I charge my batteries with a smart charger designed for multi chemistry. This shows me everytime I charge, how much current is required by the battery when the supply side is 14.4v. It requires a nearly fully discharged battery to demand over 3 amps, and that is for a voltage differential far greater that you will get from a fully charged battery, as you would get from going from batt A to B. And just to fan the fire so to speak, I did not mention chemistry. As I see similar charge currents regardless of chemistry.

This is simply not a practical matter, as UH reports from years of experience. It is a fiction from the lack of understanding of charge dynamics. These devices are not superconcuctors...

RR