Battery improvements let early submarines remain submerged longer and made surface interception less dependable. That gain primarily improved survival by allowing a boat to hide from quick-firing guns and other surface threats. It did not by itself make underwater weapons accurate, reliable, or operationally useful. A viable submarine still had to survive and attack while countermeasures were improving around it.
Notable Point · 34:05-35:27
Why better underwater endurance did not automatically make submarines lethal
Improved batteries helped submarines survive below the surface, but concealment alone did not solve the problem of attacking effectively.