Just got to thinking,
I'm adding a pre wired board with a shunt for my TM 2030 and a few other accessories , a small fuse box and a neg. bus. Do I need to ground the bus? or is it essentially an independent negative supply ..so to speak.
You should ground the negative bus - downstream of the shunt. The grounding protects the vehicle frame from being at a significantly different potential than the electrical system. This difference can occur from static charge build up or other natural phenomena.
The shunt goes between the battery and the ground connection so that ALL current going into/out of the battery flows through the very small resistance of the shunt, thus providing a measurable voltage across the shunt to your metering system. This enables the TM 2030 to calculate the current into/out of the battery, and measuring over time the AH into/out of.
I put a piece of 2 X 4 on the board to separate the "hot" and "cold" sides and kind of protect an accidental arc. 1 ground and 1 hot lead from the battery come in. The ground goes to the shunt, the hot goes to the "red" terminal. 1 lead goes out from the hot terminal to "the trailer" and the ground continues to the frame like before. Once I get the trailer back, (took it to CA.) it will only take an hour to finish the project. (install the TM 2030 monitor and a charging station) I just finished the waterproof electrical box to handle the battery cables.
So 2 leads come in from the battery. The ground goes to the shunt, then the bus, then the frame, like before. The hot lead goes to the red terminal then back out and on to the converter. A 8 ga jumper feeds the fuse box from the red terminal. Safe and sanitary