OK so I am really confused and was hoping somebody that has installed the MGL avionics RDAC can shed some light.
My problem is that the manual shows that power to the RDAC is supplied from the secured output behind the EFIS, This Is so that if your main battery fails the dedicated EFIS backup battery can still supply power to the RDAC.
The RDAC ground is connected directly to the engine (The backup battery's negative terminal is never in contact with the airframe) So how does it get grounded when it runs on the backup battery??
Am I not getting something really simple? here is info straight out of the install manuals