Per my link, I remember reading this elsewhere years ago and always thought this was the reason. My particular setup bonds the neutral and ground in the multiplus but I don't have an actual ground rod to earth. Is it possible to power the LED via induction through 1 conductor? I mean we are talking milliamps of current.
I would test by removing the ground if I was actually at the cabin where this stuff is located but I'm not and won't be for another month.
Probably because one of the ways to make an inexpensive inverter output stage requires the output to be floating.
With a normal AC sine wave of the sort you get from the wall, the “line” terminal swings between -170 and +170 V (for a 120 V RMS circuit), while the “neutral” terminal remains close to the earth or ground terminal - because neutral is actually connected to ground at one point.
You can recreate this in an inverter by generating +170 and -170 V power buses internally, and connecting the output alternately to one of +170, -170, or neutral. With this design, neutral can remain at ground, but you need both polarities of voltage.
A cheaper design is to have just a single 170 V supply, and a floating neutral. During the part of the waveform where line is supposed to be +170 with respect to neutral, transistors connect line out to +170 and neutral out to internal power supply ground. During the portion of the waveform where line is supposed to be -170 with respect to neutral, line out is actually connected to output supply ground, while output neutral is connected to power supply +170. This requires only one polarity of 170 V power supply, so it’s cheaper, but means that output “neutral” is actually at 170 V with respect to ground for part of each cycle of the output.
It is also possible to create AC at the battery voltage, using only a single polarity of supply, using either a single primary winding and a 4-transistor H-bridge (the 2nd design above), or a center-tapped transformer and 2 transistors. Then the voltage is stepped up to line voltage by the transformer. Since the transformer secondary is isolated, it can be connected with the neutral output grounded. But transformers cost money and also add extra weight.
And that’s probably why you measure voltage on neutral on your inverter: It is probably using an H-bridge type design at line voltage, without a step-up transformer."
Any relevance to our situation?