question

What is the point, the shunt when used as a battery monitor measures the current going into or out of the battery, net charge or discharge. If you added a second set of electronics to this shunt as an energy meter it would measure and report the exactly the same current flow as the battery shunt, a value you already have. As an example of the fallacy of this, if you are charging at say 50Amps and your DC loads are 50Amps, then the battery sees no current flow so the battery meter reads zero, your energy meter will also be reading zero because it is not measuring the loads.

The purpose of the DC energy meter is to measure things like your alternator charge current or DC loads and to do this it needs to have the shunt located in a different place to the battery

The problem is the "has DC system" function is a calculated value from other measurements and the measurements are not always in sync, so it bounces around. If you put an extra shunt in then yes that will help with the DC system calc, but if you use the same shunt then no it will not add anything. All the energy meter reports is the current flow through the shunt, the voltage and hence the power, i.e. it is a subset of the battery monitoring information. I have a smartshunt set up ready to be installed to track the charging current from my boats alternator for the same reason as you, to improve the DC system calc.

I’m going to trying and I will report back as to if it improves the accuracy of the “has DC system” reading. I have a few extra shunts laying around.

Ok so I did it, my son and I did the simple project of making a “Super Shunt”. we used a Smart shunt the will be set up as a DC energy meter and the Circuit board from our BMV-712 which is set up as a Battery Monitor and drilled and tapped the opposite side of the Smart Shunt.
this allow our BMV712 to function as out regular battery monitor and the Smart Shunt more accurately Meter DC power in and out of the batteries. This has helped ”stabilize“ the Has DC system on the CerboGX Display.

Not for everyone but works for us.

our install is super tight with no room for a second shunt. So….we made one perform the task of two!

Connected that way, you are NOT providing the GX device with the additional "DC system" current it needs to make better calculations. What you've done is provided a second measurement of the SAME battery DC current. If you program one device as a battery monitor and the other as the DC system current, then the DC system current will be WRONG since it is measuring the battery current not the DC load/charging source current.

It may be that the two shunts are slowing down calculations so it looks more stable.

I understand. However now the “Has DC system” is giving me a net gain/loss in watts as to what is coming out of or going into the batteries. This info is more useful than a number that is just bouncing around. Thanks for the clarification

Maybe a better solution, would be to install the shunt in series. So Shunt 1 battery port is connected to the battery. Shunt 1 load port is connected to your charge sources (MPPTS) and inverter negative and the battery port of shunt 2. The shunt 2 load port is then connected to all the DC loads you have. That way it will correctly report DC loads. Further if you configure shunt 2 to be a DC Monitor type DC system, then the Venus OS will not do any DC load calculations and use the shunt for the DC System value. The service that calculates the DC Loads value has this comment..

# Look for dcsytem devices, add them together. Otherwise, if enabled, calculate it