I would like to install an Orion XS 12/12 50A in my boat. As I understand it, the GND connection is only necessary for supplying the internal electronics, which only consume a few milliamps of current. The main current does not flow through the Orion but directly from the alternator to the battery. Can I therefore use a thin cable, e.g., 4.6 or 10 sqmm, for the GND connection of the ORION XS? Thank you for your prompt response.
The power for the electronics, as you said well less than 1 Amp, say 0.1A.
The efficiency losses, say the unit is 95% efficient at peak output, of the 50A arriving, 2.5A (5% of 50A) does not get to the domestic battery, it is returned direct to the Alternator.
Current imbalance from voltage boosting. Say you have 50A from the alternator arriving at the Orion input terminal at 13.0V, this is 650W, and the output terminal to the battery is at 14.6V. Assuming 100% conversion efficiency, 650W output is 44.5A, so tha ground wire will have 5.5A from the boost function. Amps is the rate of electron flow, so it has to balance, you can not loose matter. This current flow can get quite large if there is a lot of voltage drop between the engine and Orion.
This means the ground wire needs to handle of the order of 0.1+2.5+5.5= 8.1A.
In practical terms you are correct, the ground wire can be smaller, but voltage drop is still important as this provides the reference point, so use something like 6 or 10mm2 cable.