
We all know about the large XXI and smaller XXIII costal electro u-boats that came along during the last months of the war. The XXI was indeed an awesome machine and the Allies were in for a lot of trouble if it had been ready earlier.
The idea of the XXI and XXIII was born during an otherwise depressing meeting between the U-bootwaffe and professor Walther in November 1942. The meeting was about progress in the development of the Walter U-boats, which had a complicated but promising propulsion system. The message was depressing: As usual the Walter U-boats were postphoned and they were still far too expensive in fuel.
However, during the meeting two German engeneers Schuerer and Broecking had a bright idea: If the streamlined hull of the large Walter U-boat was filled with three times the normal battery capacity, the fast electroboat was a reality. The rest is history, as they say.
Now, what-if the Germans decided to spice up the existing U-boats and fill them up with batteries too to improve their underwater performance? It would be a stop gap solution until the real electroboats came off the line but I believe that it could have been implemented almost at once.
Think of this: The large 1,819 tonnes (submerged) XXI electroboat had the following specifications:
17.2 knots submerged top speed
340 miles range under water at 5 knots
4,400 horsepower submerged
372 battery-cells type 44 MAL 740, in total 33,900 Ah
The large 1,232 tonnes (submerged) IXC/40 conventional U-boat had the following specifications:
7.3 knots submerged top speed
63 miles range under water at 4 knots
1,000 horsepower submerged
124 battery-cells type 44 MAL 740, in total 11,300 Ah
Now, if the Germans had decided to increase the battery-capacity of the IXC/40 in late 1942 by, say 50%, it would solve many of the types problems in 1943 and 1944 (especially if a schnorkel was added). Adding 62 batteries to the existing 124 should have been possible by some minor rearangement of the interior decoration. The IXC/40 had 24 torpedos. Reducing that to 20 would free up a lot of space for more batteries. Other modifications which would find more space for batteries were probably also possible.
With 186 batteries, the IXC/40 specifications might look like this with a 50% increase in capabilities:
11 knots submerged top speed
95 miles range at 6 knots
1,500 horsepower submerged.
Increasing the top speed and range by 50% would more than dubble the area the Allied anti-submarine forces would have to scan. By early 1943, the Allied anti-submarine warfare would be much less effective and the U-boatwaffe much more dangerous.
What do you think?
More on batteries here
http://uboat.net/technical/batteries.htm