Japan's Silent Submarines Extend Range With Lithium-Ion Batteries (nikkei.com)
AmiMoJo shares a report from Nikkei Asian Review: Japan's first submarine powered by lithium-ion batteries was launched on Thursday. The [Soryu-class diesel-electric] submarine can reach speeds of roughly 20 knots and displaces 2,950 tons. It will be delivered to the Japan Maritime Self-Defense Force in March 2020. Batteries are recharged by the energy generated by Oryu's diesel engines. The vessel switches to batteries during operations and actual combat in order to silence the engines and become harder to detect. The lithium-ion batteries radically extend the sub's range and time it can spend underwater.
You better email those Japanese engineers right away to inform them of the terrible mistake they made, that only you can see.
When all you have is a hammer, every problem starts to look like a thumb.