So I stumbled on an interesting HEI phenomenon

One question I'd have is where were you measuring the voltage? And do you know what the drop is actually right at the HEI?

On the other end, "all this stuff" seems to have a low limit.

One of my big bitches was back when I used to be more active in amateur radio. I believe the worst as I recall was my Yaesu FT- 890. Dam thing did NOT like low batt. voltage---exactly what you might "have" if you were in some emergency situation, or even just "operating portable"