Taigei's LIBs With More Powerful Kawasaki Diesels

Lithium-ion Batteries (LIBs) can be recharged to a higher total capacity and more quickly than Lead-acid Batteries (LABs). But to do this LIBs require more powerful diesels. So Japan has been installing more powerful Kawasaki diesels in its new Taigei-class submarines. 

Wispywood2344 on September 24, 2022 commented + some additions by Pete:

Japan's Soryu Mk.1s [see table below] are equipped with LABs and use conventional diesel gensets [that are likely 2 x 12V25/25SB diesels, each of  2,120kW = 4,240kW maximum power] see table below]

But the LABs can only absorb 60-70% of maximum diesel power - amounting to 3,700 kW (= 2 x 1,850).

This results in an Indiscretion Ratio (IR) of about 9-10% at an average speed of 4kt. This is without using the Soryu Mk.1's Stirling engine AIP. 

The Taigei-class submarines use LIBs instead of LABs. These LIBs can be recharged to a higher extent than the diesels to LABs 70% rating and more quickly. 

The Taigei's likely 2 x 12V25/31S diesel gensets can be run [at a maximum 5,520kW (= 2 x 2,760) with almost all absorbed by the LIBs. This represents 50% more than the Soryu Mk.1's  previous 12V25/25SBs working with LABs [1].

As a result, LIB charging power is greatly increased and the IR, at an average speed of 4kt, is reduced to about 4-5%. 

Pete Comment

More and more countries are adopting LIBs for their submarines, but to quickly recharge the LIBs to their fullest extent requires much more powerful diesels. The world's most common submarine diesel maker, MTU, might need to learn from Japan's Kawasaki what level of genset power will be required. Will MTU 4000s be powerful enough? 

[1] More informations see Japanese Ministry of Defense's Technical Research and Development Institute (TRDI) specification "New Snorkel Generator System (Part.1)". p.10

TABLE

Submarine Matters' Oyashio-Soryu-Taigei TABLE as at October 4, 2022.