Growatt 24V only displaying half the incoming Watts?

[solarcastiron]

720W of 4x 180W GrapeSolar panels on van.
All my wiring is correct, as far as I can tell anyway.
Previous GoalZero Yeti all-in-one displayed correct Watts, going over the 720W to produce 760W in full sun with clean panels.
The voltage is correct on the Growatt, 77V-86V. All panels are in series.
The Amps does not seem to be correct. At full sun it shows 12 or 13 Amps.
The wattage is showing precisely half the incoming Watts, 380W. Half of 760W.
It's NOT because the batteries are full. Even when batteries have been at 20%, still the same result.
If I put the system under full load, it doesn't impact the displayed incoming watts.
I've had this setup 2 years and it's always this way. I'm just getting around to wanting to sort it out.
This doesn't compute!

Is this a characteristic of the Growatt? It does seem to be actually pulling the full ~720W even though it's displaying exactly half at all times.

If not, what could possibly be wrong here?

I feel like the only way to test it would be to buy another solar charger and see what it displays, but I'd rather not.

 

[Mattb4]

What is the incoming displayed voltage when you get the displayed wattage? Is it possible the amperage you are reading is the PV amperage and not the charge amperage? W=VA Also check your charge amperage (and voltage) when you have no load other than battery and see if the math works pout.

Though it is possible your AIO has a bad current sensor. My PowMr is slightly inaccurate in this regards. It is why I run a separate PV shunt and meter.