While recharging try to move at low speed or even remaining stationary.
Anyway, I wouldn't use my batteries to "travel" or "patrol". If "air traffic" forces me to remain submerged I "crawl" at 1 knt (and I use that as a "home rule" to represent energy consumption to support varius electrical subsystems and the fact that WWII subs couldn't maintain depth without some speed). I always try to maintain a 85-80% "charge" on the battery. You never know when you're going to need it!
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