Ammeter voltage drop

What type of ammeter?
Nothing in the system should show any measureable resistance.
If there's a 0.1 ohms in the whole line between the battery and main splice, I'd say that's not a good start.

Measured three in this post.
Charging system road rage

My terminology may not be correct. It may not really be an internal 'shunt'. Those ammeters work on magnetic field created by the current through the metal plate. I think more properly a shunt type has a parallel path. Regardless, an in-line ammeter should have no resistance.