some observations:
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A- this looks fine, but I've had issues with this style of breaker switches getting hot causing volt drop when pulling current - so keep an eye on it . . . if it starts to get hot swap out for a MIDI or MEGA fuse.
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B- is this the main chassis ground connection in yellow? - of so the green? should be both the LB1 + LB2 NEG feeds.
both battery NEGS need to got to the SHUNT, then one common GROUND from the SHUNT to the van BODY. Also the gauge of the cable needs to be the same thickness as the main POS as it will be carrying the same high current . . . so if you use 150A cable for the POS, then you need 150A cable for the NEG . . .
if 2x 150A POS then you need 1x300A for the main NEG from the shunt ( same as you have done with the main starter battery feed)
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C - where is the second battery? - each battery needs a fuse next to the POS interlink cable.
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D - Fuse should be on the POS side of the battery. (technically it could go on the NEG side, but depending on the circuit layout the power could fin an alternate route to ground so POS is always best place)
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E - the second LB2 should have a direct connection to the shunt, it can go to either the LB1 or the shunt, whatever is shortest.
yellow or blue is ok, red is not right, the shunt will not read the power correctly.
F - where is this master switch in your schematic?
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G - can you post a pic of your starter battery NEG terminal and connections
H - Inverter NEG connection needs to do direct to chassis ground, same as all you loads NEGS to chassis. . . ONLY the LB1 & LB2 NEGS to shunt - then shunt to chassis. credis to
@Grim Reaper for spotting that one.
I - Fuse layout - this is where the fuses would normally be, as close to the battery POS connections as possible.
J -