My Progessive Dynamics Converter will charge the batteries to 90% capacity in 8 hours or less depending on how far they were depleted and full charge in 11 hours.
If I was driving 8 hours (with the alternator charging the batteries) and then stopped and ran the generator for another 3 or 4 hours, my batteries would be at or very close to a full charge.
So yes, if we want to be technical about it and batteries have been depleted enough that the Converter Boost Mode has to kick in, then it could take 10 - 12 hours to fully charge and the generator would need ot be running that long.
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