Originally Posted by Alex W
On a diesel engine (and probably the A4 too) nothing will happen if you disconnect power while the engine is running. The battery is only used at startup to turn over the engine.
The switch needs to be close to the batteries to be practical. You could make a cover for it though. I haven't tried, but I'd guess that a double gang outdoor outlet cover might fit over most battery switches.
Unless the battery switch has an AFD (Alternator Field Disconnect), you can smoke the alternator if you switch it to "OFF" while the engine (diesel or gasoline) is running.
In fact, if you look at many of these older "1/2/BOTH/OFF" switches, they often say right on them, not to do this. See this photo:
PERKO Battery Switches at West Marine
Newer ones have the AFD, and you can do whatever you like. Note in the WM ad, you can choose with or without the AFD function.