"w_tom" wrote in message
...
If switching from a weaker bank of batteries to a fully
charged bank, then the armature coil inside alternator cannot
discharge fast enough. Load dump results.

Both SAE J1455 and ISO 7637-1 defined load dump for 12 V
automotive alternators as up to 270 volts and energy up to 50
joules.

You can certainly get this when switching from a discharged battery to
"OFF".

Even a fully charged battery will absorb a tremendous amount of current if
the voltage rises very much. If the battery is any good, I doubt that you
could get the voltage up above 16 volts. Just the capacitive load of the
battery could absorb a fair amount of the energy.

The problem occurs when the alternator was pumping amps into the battery and
it is switched to OFF. It is a basic inductor problem, the current can't
change instantaneously. It WILL go someplace, and it is likely that it will
damage things in the process.

Rod