All loads on the battery must be wired to go through the shunt.
All vehicle grounds must be fed through the Shunt, if any wires /cables go directly to the battery (-) that does not go through the shunt, then the trimetric is not reading all the loads on the battery
Batteries===========//SHUNT\\===========ALL Loads (-)
..........................................................................All charging ==
..........................................................................All vehicle grounds
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;Negative Bussbar
If any wire goes directly to the battery (-) which does not come from the battery side of the shunt, then the current will not be counted by the trimetric.
I took the original starter battery to engine ground, and made that my engine to shunt ground. My frame/ Firewall to starter battery ground became my Frame/Firewall to Shunt ground.
This way My shunt sees alternator current. Anything that is grounded right to the frame will be counted by the trimetric.
The ground is shared between both starter and house batteries. Anything grounded directly to the starter battery is bypassing the shunt and not being counted.
Make sure to label the wires so that the there is no condusion as to which cables goto the battery from ONLY the battery side of the shunt . All other cables to the LOAD side of the shunt.
Many stock lights and perhaps the stereo is grounded right to the frame, or firewall. If the starter battery bround does not go through the Shunt then this current is not counted by the Shunt/trimetric.
Only if you are not doing any alternator charging of the house battery, AND all house loads and
only house loads are run through the shunt, will the trimetric be accurate.
If the trimetric has an 'amp hour from full' screen, try to use that rather than the percentage remaining. Battery capacity is always shrinking as they age, so the Percentage will be off unless the total amp hour capacity is lowered and actually represents the actual remaining capacity. Reliance on percentage remaining Screen is unwise.
Even when wired properly to monitor ALL current into and out of the batteries, you can only really expect 90% accuracy, at best. Throw really high amp draws in there, and that figure drops.
The sense wires leading to the shunt from the trimetric are sensitive to interference. Did you use twisted pair wire? It does not appear to be. Twisted pair is not just two wires twisted. It is two pairs of two wires twisted. Any 120Vac lines in the area should not run parallel with the twisted pair sense wires and certainly not in direct contact. Where they have to cross each other, 90 degree angles. Basically you want the twisted pair sense wires as far as can be from all other wires carrying current. Obviously this is difficult to achieve perfectly, but some distance and crossing at 90 degrees helps greatly.
Also some 12v loads can cause interference on these sense wires. Twisting the (=) and negative two wire, tightly in a drill helps reduced interference.
You can also take additional steps like wrapping the twisted pair in aluminum tape and grounding the aluminum tape, or run them in metal conduit.
I have the same shunt. That one Store bought cable on the bottom of your shunt. That is a steel connector. It is a very poor connection.
A quick story about that store bought 4awg cable. I had two 4 awg wires from shunt to house battery in parallel. One cable had those steel ring terminals, the other had a higher quality copper connector crimped on.
I put my Clamp on Ammeter over both these cables. 4.2 amps were flowing from my house batterie at the times. Then I Put the clamp on Ammeter over just the store bought cable with steel ring terminals . It was passing 0.7 amps. I put the Clamp meter over the other 4 awg cable with the copper ring terminals, and it was passing the remaining 3.5 amps. I cut off the steel connectors, used my Hydraulic crimper on some new ring terminal lugs, and remeasured. Both cables were now sharing the load equally.
Here are those highly resistive stamped steel ring terminals (notice the rust?) I replaced, sticking to a magnet. These also suffer quickly from corrosion in a flooded battery environment not only due to to charging gasses, but just the dissimilar metals, as the copper is just crushed inside the steel then a hole is drilled through it.
Also SAE store bought battery cables are narrower diameter than AWG rated wires, by upto 20%.
Genuinedealz will make you up high quality cables if you do not have the proper tools for crimping. Those steel connectors are just problems waiting to happen.
