🚀 go-pugleaf

Actually, the phenominom is called "load dump". I am a former
Delco EE, and we had to protect against load dump.
The alternator, cranking out full tilt, spikes to about 80V
for several hundred milliseconds, until it's field current
dies. This happens when you disconnect the alternator from a
heavy load. The other car starting may have this effect. one
way to avoid it is to jump with your engine off, or at least
turn it off before disconnecting.

Don't forget to connect the - cable somewhere else on the car,
no to the battery. Sparks during disconnect can ignite any
hydrogen the battery has generated.