Battery current during engine start

SCVJeff wrote:

Salvo wrote:
For the heck of it here's the starting current from my new toy: '16 Miata.



Charging current slowly increases to about 30A after 8 sec.

That ripple out at 200A was what I was presuming was the back EMF of the starter coil collapsing

:h Why would the solenoid field collapse while the starter is apparently still turning? I'd guess that the ripple there is more due to the starter motor hitting up against a compression stroke on the engine. That would also explain why each successive peak is a little less severe, as the engine gains momentum. The waveform does look like ringing, though, I admit.

I suspect we don't actually see the solenoid ripple because of a couple of possibilities things: there may well be a snubber rectifier to shunt it away, and even if not presumably the opening of the starter keyswitch (or equivalent) disconnects it from the circuit being measured. In the latter case, without a snubber, I would not be surprised if there is some arcing in the switch.