Deep Cycle Battery Charging From Alternator

jharrell wrote:

MEXICOWANDERER wrote:
And do not forget to add the effects of the starter solenoid itself. A large field collapse can definitely be felt. It is a magnetic servo as well as electric contact controller.

This seems to be mostly what is found when talking about any kind of spike from starting due to anything powered off the starter switch during cranking and would be the same with a loaded or unloaded starting motor. Instead of a flyback diode on solenoid it seem a starter relay is used to drive solenoid and that relay may have built in diode, but its even smaller coil too. I would imagine in cars with remote/push button start there is transient protection on the solid state circuit controlling the starter relay.

I don't know maybe modern starters have flyback diodes since they are so easy to add but no one seems to talk about it or care the main issue seems to be arcing and RF not giant spikes like you would see from a load dumped alternator.

Definitely want to get a scope on my starter system and see how large the spike is at different point to see how well my batteries suppress it.

Also ... you might want to jumper from your vehicle A to your vehicle B with the typical large gauge jumper cables and then start vehicle A a few times with vehicle B left running. And while repeating the test starting sequences, alternatively put your o'scope (of course using the scope's AC probe) between the plus and minus terminals of the starting battery on both vehicles, in turn.

I'd be very surprised if you see any high frequency spikes on the screen on either starting battery's terminals during the test starting sequence. Automotive battery terminal voltage doesn't tend to be jerked around by high frequency spikes originating elsewhere in a vehicle's systems that might be connected to the starting battery via relatively small gauge wiring.

I believe that it's pretty difficult - if not impossible - for spikes from one vehicle's systems to be transferred to another vehicle's systems when they're only connected via large gauge jumper cables connected between their starting battery's terminals.