I think if you accept that upon surfacing your automatically in charging mode....the only time you might want to consider changing straight over to standard is if your in hot persuit of a convoy that has passed you by.
I shudder when I think of the times when I've surfaced and shortly after have had to submergs again because an escort has spotted me or an aircraft suddenly appears as if from nowhere.
Those few extra % points of charge can make the difference between sneaking away or having to lie 'doggo' through lack of power.....as we all know this is of no benefit in the SH3 world.