reading up on the sub, just because it is interesting:
Type XXI Electric Boats
372 cells 44 MAL 740 (
33900 Ah)
for use in the type XXI
Type XXI Elektro boats - U-boat Types - German U-boats of WWII - Kriegsmarine - uboat.net
recharged in 3-5 hours via snorkel once every 2-3 days. could go 340 miles @ 5 knots submerged.