Annoying PWM sound from Xantrex inverter

CJW8 wrote:
Think of a battery sense line as the same as a meter lead. Meter leads are very small wire and yet the meter reads very accurately. This is because there is no current flow. Some better charge controllers use this to sense the realtime battery voltage rather than just pull the voltage reading off of the controller output.

Right, that makes sense. In some respects thought the controller-battery system is self correcting when it comes to voltage readings: when the battery is approaching float, the current is slowing and so the readings become more accurate even when taken from the controller output (since the main distortion in the voltage at the controller output is current induced voltage drop, as far as I know).

While not ideal, my MPPT controller is connected to the inverter input for convenience. I have the same inverter as you and there is no noise...ever, no matter what stage the controller is in.

Thanks for the data point! My noise may be related more to my particular wiring setup, than the inverter. I do notice a small amount of noise from the same battery/inverter area when I have my LEDs on PWM, and the solar controller is off.

I even bought an oscilloscope to help narrow this down (and, well, because it was an excuse to buy an oscillscope). Then, I put the bed back on - I had to remove the bed in the back of my van to get at the installation area - and that muffled the noise to the point where I just don't hear it. Occasially when I open the back doors, which have a direct line of sight to the inverter, I hear the noise and am reminded of this thread I started and the oscilloscope I haven't unboxed yet :)

As a final note, I installed an toaster oven in my rig as well. When I leave the oven plugged in, I often hear a buzzing from it, even though it is off. That seems to happen even when my solar is off, so I guess there is yet another noise source on the 120V lines.