Thanks very much to jimbonzzz for his schematic, which if I'm understanding it properly says the black wire next to the green one in a standard female RJ-11 wall jack should be ground (the green being +12v). But I'm having a problem.
I'm trying to use the V1 hardwire adapter, which is connected directly to the battery on my BMW motorcycle, as a way to connect a low-current battery tender (1.25 amps). My volt meter shows +12v between the green wire and any frame ground. But none of the other wires show as grounds. The goal here is to be able to connect the float-charger without removing any body panels to get at the battery terminals.
If I connect the battery tender plus lead to the green wire (plugged via the V1's coiled cable into the hardwire adapter RJ-11, not the accessory port on that adapter) and its minus lead to the frame, the tender shows via its LEDS that the connection is correct and the battery is charging.
Anybody know why I might be "missing" a ground? The V1 works fine when connected to this same adapter.