I managed to sneak out one of the current sensors. Did I mention corrosion?
Cleaning it up didn't fix the issue, though with it disconnected, my battery bars came up on the instrument cluster.
So it was back to pulling the battery.
After pulling half of the interior apart, just to get at the two back bolts on the battery, I found the ground connection for it all, and cleaned it up.
One of the bolts gave me a fight:
Who knew a 1/4" driver could break a bolt that big?
Showing the battery my opinion of it after tearing apart the interior and fighting a seized bolt:
(Mod, feel free to delete it if it's too spicy for this forum)
I was expecting orange sticks:
Those are distinctly yellow. They've been replaced at some point.
Tonight, we'll pull that second current sensor apart and see how messed up it is...then order replacement parts if a good cleaning doesn't fix it.