12 volt wiring

[BCBrad]

I am trying to make sense of the 12 volt connections where the batteries tie in. This looks like a bus bar with red wire from converter and bigger black wire from battery compartment. The smaller black and white wire are a mystery to me. Seems like you would have 12V to anything connected to this bar.

[Salty]

That brass buss bar is actually a shunt. The black and white wire would go to an ammeter.

https://en.wikipedia.org/wiki/Shunt_%28electrical%29

[Razorback]

Isn't "bus bar" a good description? The pictured bar is a common 12V point, right? A shunt goes around something.... that bar is tying all of those connections together.

[Salty]

Use in current measuring
An ammeter shunt allows the measurement of current values too large to be directly measured by a particular ammeter. In this case, a separate shunt, a resistor of very low but accurately known resistance, is placed in parallel with a voltmeter, so that virtually all of the current to be measured will flow through the shunt The resistance is chosen so that the resultant voltage drop is measurable but low enough not to disrupt the circuit. The voltage across the shunt is proportional to the current flowing through it, and so the measured voltage can be scaled to directly display the current value.

Shunts are common in Welding and Plasma power supplies where the high current used would negate the use of a standard Ammeter. These are old devices and out of favor. Accurate, but out of favor. Now we use Hall effect sensors to measure amps flowing through a circuit

[BCBrad]

Perfect answers. Thank you!