The voltage readings sound fairly normal to me. Also, since you don't get fluctuating voltages depending on RPM, I would suspect the voltage regulator is also good.
I would check elsewhere. Electrical short maybe, or failing electric steering box, or ECU?
There was no big spark, my car is a 2.6 VW Microbus 2006 and his car a 1.4 Reno clio or something. His negative cable melted, and was smoking after I had:
1) Checked to see if I could roll start it - didnt roll start - or have any lights turned on - completely dead.
2) Started my car,
3) Then connected jupmpers
4) Then went to his divers
5) Tried to turn it ...
The correct way to jump start: put red jumper cable to positive post or remote positive terminal on discharged vehicle. Attach other red clamp to working vehicle. Attach black cable end to negative post on dead battery. Attach other black cable to engine ground on working vehicle. As mentioned, it is risky to jumpstart newer cars.
If you connect a set of jump leads the wrong way, you're likely to see a pretty big spark as you connect the last one - even if the battery you're jumping to is completely dead, the alternator's diode pack can carry a couple of hundred amps. If there's a fusible link for the alternator that will fail pretty quickly.
Most likely, the car won't even crank, ...
It is possible to damage an alternator during a jump start and even after a jump start. The voltage regulator is solid state so any voltage spike from the finall connection spark can fry it. That doesn't necessarily mean you perform the jump improperly. Usually crossed polarity fries the fuses. Also, if you jump start the dead car and let it run, the alt in ...
If you did it the wrong way I would expect the main fusible link to have blown on one or both cars.
If the alternator failing is not the reason they needed the jumpstart in the first place, alternator failures are very common if someone drives the car trying to use the alternator to charge the battery all the way up from dead. Alternators are designed to ...
30 amp rating is the capacity of the relay, take it past that rating and it burns up, go for the dead mans switch or a commercial battery Isolator, example here
Generally you want the amp rating slightly higher than the max output of the alternator.