My board needs 0,17A in S3 Mode (measured incl. M2), 0,11A in off mode and about 3,3-3,8A on.
That means with my 60Ah battery it should last 60/0,17= 353h = 14,7 days in S3 and about 17h comlete on.
But I'm almost sure, when the M2 cuts off because of an voltage under 11V to prevent deep discharge of the battery, there will be too less energy left to start the engine, especially if it's cold.
Some other experiences?