Good description, Jon.

Some observations: when the charger is on, ac input to the circuits powered by that inverter seems to be passed through to those circuits. When the charger is off, the inverter seems to power those loads. On my charger #2 that does not seem to be charging, when I turn off the charger, the ac load displayed on my control panel drops approximately .3 amps. Turn the charger on and the ac load goes up the same amount when the ac input kicks in. Interestingly, there is enough of a delay (measured in milliseconds probably) in the switch from ac power to inverter power that sensitive items, like a powered usb hub or hard drive, will disconnect from the computer. Nothing else seems to notice, like a refrigerator or a lamp on an outlet.

The remote panel seems to be doing a fairly accurate job of measuring ac and dc loads, so if charger #2 doesn't show any charging load similar to charger #1, then I would assume that it isn't charging. I can't readily get to my house batteries so I can't verify that.