[thingstodo]

I have two of the "Durafied 1350W continuous, 2700W peak Inverter S1350DI" inverters. I have not dug out any more of the surplus units.

I connected each of these inverters to a 12V battery (a small one) to check out the isolation between the DC output sections.

As seen in my crude but readable sketch (I'm trying out google docs), I checked out the voltage of each inverter separately. The voltage starts out wandering a bit, but settles down to a small range of 140 - 142.2 VDC. Both inverters have this voltage (internally). I was not able to reproduce the 135 VDC that I had measured earlier. Nor was I able to have the inverter 'go to sleep' and disable it's output.

Prior to connecting these inverters in series, I checked the voltage between the + and - terminals on the battery with the + and - terminals on the 'output'. The voltmeter showed a consistent readings. If points in a circuit are isolated, you can see many voltage differences but they are somewhat random and not repeatable. - battery and - output were solid at 0.0VDC. I'll reference everything from - battery. + battery is 12.6VDC as expected. + output is 140 - 142VDC. The output is NOT ISOLATED from the battery at ALL.

In my excitement, I had assumed that boost transformers meant that the input and output were isolated from each other. This was a rather dangerous assumption. It is good that I checked it out as early as I have.

My confidence is a bit shaken - and my resolve to check absolutely EVERYTHING is much stronger.

On the agenda for tomorrow - power the inverters from separate 12V batteries, verify that the inverters can be connected in series to get about 280 VDC, and connect this voltage up to a test VFD to ensure that it powers up as it should.