bummer.
i wouldn't even think of going after a convoy with escorts if my batteries are less than 50%. you never know how long it's gonna be before you get another chance at recharging them after evading the escorts,and that's the bottom line.
don't know what mod(s) you are using, but in most, along with stock, you can recharge batteries, surfaced,all stopped,preferably at night. it's not too bad if you use time compression, and certainly saves on your diesel reserves.
this may not be 100% historically accurate. i'm pretty sure they had to be running diesels at some speed, surfaced, to recharge them. uboats had snorkels later in the war for this purpose, along with restoring their O2 supply.
i think that's what they did anyway.
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