Deep Cycle Battery Charging From Alternator

MEXICOWANDERER wrote:


If transient voltage events are rare and of little consequence why has General Motors, Nippondenso, and other manufacturers spent hundreds of millions of dollars converting all power rectifiers in their alternators from standard silicon to TVS snubber avalanche 28-32 volts? GM did it in the late 1980's. They also redesigned the 1116411 voltage regulator, then the 425 then the 437. Each update included one more TVS. Was it a mistake? All the avalanche and TVS devices?

I thought this was for load dump protection if the the battery where disconnected from the alternator while running, this is where you get 120v spike right into the rest of your electrical system. This is like worst case situation, where someone was nots smart or something really bad happened like loose battery contact.

with a starter motor you have the solenoid breaking the circuit, and on the coil of the solenoid you have a more likely TVS issue because you might have something sensitive after the ignition switch, but not usually. Otherwise both the ignition switch and solenoid are opened up and you get some arcing on the contacts without flyback diodes and a little spike that the battery easily absorbs before it gets back to the DC bus.

This isn't my area of expertise, but not sure where you see big spikes like your talking about. I mean yeah put your fingers between solenoid and motor, but how does it jump solenoid other than arcing? Is it because it pulling down voltage on negative side? Can't really find anything on that, and it doesn't seem like TVS diodes are used on starters and ignition coils that much, but some people add them, and it seems mainly to reduce arcing to keep contacting lasting longer and maybe reduce RF.