I think we’re arguing over two different events. In a typical SH bird, that has one switch for Bat-1 or Bat-2, all power will be shut off for a brief moment as batteries are switched.........Yes, this will cause a voltage spike as electronic fields collapse across coils, etc in the radio and other electronic equipment, that was drawing about 2 amps before the power was removed. Several ways to prevent the momentary power loss have been recommended and I believe they will all work!

The procedure that Hank, Chip and I use does not remove all power, it only adds about 2 volts to the power supply! We turn on the fresh battery with its own SPST switch, just before we switch off the low voltage battery with another SPST switch. I have tested this and observed no voltage spike, and read 300 m/a (1/3 amp) as the fresh battery tried to recharge the low battery. This event is little more that what the old “voltage regulator” did when cars had generators. The voltage regulator would shut off generator voltage when the battery was fully charged, then turn on generator voltage as it sensed the battery voltage was getting low. The same event occurs when your buddy offers to “give you a jump” when your car won’t start. Using jumper cables, he adds about 2 volts to your car battery.
Does this help to put to rest this never ending argument?
JJ