[zinc_00_gt]

I run thr same charger and currently have the same noise.
The noise you hear is a improperly adjusted bypass valve.

In the center of the valve thier is a adjustment nut that controls the butterfly valve inside the bypass unit. I think it's a 8mm nut but am not positive.

Just make small adjustments till the fluttering goes away.

I had to adjust mine a couple time in the last year or so.