If you have rough weather, then of course... it would stand to reason, that it would take somewhat longer, to recharge the bats...
seeing as how until the schnorkel, the intake/output stacks for the diesels... are there, on the outer sides of the Uboats.
Any good waves, caused by rough weather, are going to interfere with intake of air, to supply the diesels with 1 part of the necessary components for them to run... namely, air. That would also include causing an interruption in the outbound flow of the exhaust, as well.
Rough weather, would also end up, impeding forward motion, as well as the ability to stay on track... aka course, too.
This, was highly mentioned in Das Boot (the movie, not that sad sack tv series...
by the navigator... what was his name... Kriechbaum... when questioned by the Kaleun about what their positioning was... & Mentioned that due to the overcast conditions, the rough weather... of NOT being able to take a decent sun/star shot with the... sextant... to get a proper positioning report done.
Just... food, for thought...
M. M.