I spent most of the day today researching various RV power outlets, NEMA connectors, and extension cords. Despite having an engineering degree, I was still pretty clueless about electricity. I am learning. And now I know just enough to be dangerous!
Today I finally understood what a "bridged adapter" is, where it is used, and why it won't work for the rapid charger.
This is how the 240V outlets work:
Split-phase electric power - Wikipedia
And this is the schematic:
The 240V outlets are in effect two 120V outlets with a common (neutral) wire and two hot wires. The two hot wires produce the 240V power. This is what we need.
But you can also draw 120V power from the same outlet, as shown in this picture. Two circuits. And this is exactly what the big 50A RVs do.
But when these RVs arrive at campgrounds that have only 110V 15A outlets, they plug in those adapters that have the two Hot legs "bridged" or connected together. This way both of their 120V circuits are connected to the same two wires -- the Hot and the Neutral of the 120V 15A plug. This is what a typical RV "dogbone" adapter looks like:
Or like this, if they are using a generator cord:
The two hot legs are bridged, or connected together. If you use this thing to plug in your Rapid charger, nothing will blow up, but it will not work either.
This is how I would wire it (below, the red/black color have been updated)). The Neutral leg of the 4-post NEMA L14-30 connector (usually white wire, but I marked it gray) is not connected to anything. Do not try this at home, unless you understand what you are doing.
I hope I got this right.
