[warbirdfan]

I'll throw out another view and observation on the subject. The attached pic is from my Zone. The bottom battery in the pic is on the passenger right side. The volt meter is to the right of the bottom battery mounted on the kick panel on the other side of the body.
My charger is hooked up as shown. The red collar is the positive on the top right battery and the black collar is the negative post on the bottom battery.

The red wire attached to the positive post is the charger wire along with the white and black wire that is attached to the negative post on the bottom battery.

Note the Green wire isn't attached to anything.

Note the heat sink to the left side of the bottom battery. That is the DC to DC converter. (48v to 12v) The harness is buried down between the bottom and top battery. I suspect that is the source (harness) for a 12v radio power supply.

Note tow switch to the left side of the converter for reference.