Japan Just Launched Its First “Big Whale” Lithium-Ion Battery Powered Submarine

After around a decade of research and development, Japan is now close to putting into service the first of a new type of diesel-electric submarine, driven by an innovative propulsion system using lithium-ion batteries. While the two most recent examples of Japan’s Soryu class are fitted with a similar powerplant, the Taigei, which means Big Whale in Japanese, is the first of a class to feature it from the outset. Currently, only Japan is known to have operational submarines with lithium-ion batteries.

The Taigei was launched on October 14, 2020, at the Mitsubishi Heavy Industries (MHI) shipyard in the city of Kobe, in the western prefecture of Hyogo. The event was attended by Japan’s Minister of Defense Nobuo Kishi and Japan Maritime Self-Defense Force (JMSDF) chief Hiroshi Yamamura. 

Reports suggest that construction of the boat cost around $710 million. The new submarine is 275 feet 7 inches long and with a surfaced displacement of around 3,000 tons, it is also the largest post-World War II submarine Japan has built. The existing Soryu class design has a surfaced displacement of approximately 2,900 tons. 

The Taigei can accommodate up to 70 crew. At the launch, the JMSDF also noted that the new sub will offer a “suitable environment for female submariners,” after the first woman entered the Japanese submariners’ academy earlier in 2020

However, by far the most innovative part of Taigei’s design is its advanced diesel-electric powerplant, which as noted, makes use of lithium-ion batteries. The last two boats in the previous Soryu class were completed with a similar configuration, which is claimed to provide increased endurance at high speeds when submerged. Charging is also said to be quicker and battery life longer compared to lead-acid batteries, which have to be repeatedly recharged by running the diesel engines. Besides, the lithium-ion cells are less bulky and have reduced maintenance requirements. 

On the other hand, lithium-ion batteries are more costly than the lead-acid alternative. In the past, the JMSDF provided a construction cost of $488 million for a standard Soryu-class boat, as opposed to $608 million for the first of the lithium-ion subvariants.

Back in early 2017, The War Zone’s Tyler Rogoway looked at the benefits of lithium-ion batteries, which not only offer advantages over traditional lead-acid cells, but could challenge Air Independent Propulsion (AIP) technology for use in new-build submarines overall.

At that time, it already appeared that Japan was seeking to entirely replace AIP technology, which comes in multiple forms, with a new propulsion arrangement centered around lithium-ion batteries that would still retain the same advantages. A key consideration was further reducing the submarine’s acoustic signature by eliminating the many moving parts typically found in AIP systems, which are already generally very quiet.

In principle, this would result in an exceptionally quiet boat, making it very hard for opponents to detect and track, but with the added advantage of being able to accelerate much more rapidly while submerged than existing AIP submarines. Those factors indicate that the JMSDF could be prioritizing dash speed and stealth as a means to counter the PLAN’s burgeoning nuclear-powered and AIP-driven submarines.

On the other hand, potential problems with lithium-ion batteries include the fact they can be prone to combusting, generating a lot of heat, plus toxic fumes and conductive dust, all of which raise the risk of potentially deadly fires and other accidents. As such, there is a need for an additional degree of safety to be built into the submarine’s basic design.

It certainly seems that the JMSDF has greater confidence that the new propulsion system will live up to its promise and that any safety concerns have been addressed. The later Soryu boats incorporate a specialized automated fire-extinguishing system and it can be assumed that something similar is used in the Taigei too.

JMSDF submarine Soryu is pulled away from a submarine tender off Guam. The last two boats in its class are already equipped with lithium-ion batteries., U.S. NAVY/MASS COMMUNICATION SPECIALIST 3RD CLASS RANDALL W. RAMASWAMY

Taigei will also be used to further prove this propulsion concept, in general. In December 2018, the Japanese government published a white paper entitled National Defense Program Guidelines for Fiscal Year 2019 and Beyond that said the submarine would be used primarily for testing of the new technology. This could help explain the dramatic acceleration of Taigei’s development and construction. MHI had announced plans to build a new type of diesel-electric submarine in June 2019, initially known as the 29SS class. At that point, construction was anticipated to begin between 2025 and 2028, followed by the launch of the first vessel around 2031. After completing its fitting out and at-sea trials, plans now call for the Taigei to deploy operationally with the JMSDF in March 2022 in its testing-focused role.

The Taigei and the other future submarines in its class are just one part of Japan’s broader efforts to bolster its defenses in response to growing regional security concerns. This includes the increasing threat posed by China’s military, especially its fast-growing navy, as well as by an ever-more capable North Korea, which recently unveiled a slew of new weapons, including new intercontinental and submarine-launched ballistic missiles.

With an eye on a spike in activity by the People’s Liberation Army Navy (PLAN) in both the East China Sea and the South China Sea, as well as further out into the Pacific, Tokyo’s defense plans include expansion of its submarine fleet to 22 vessels by the early 2020s.

Currently, the JMSDF operates nine 2,750-ton-displacement Oyashio-class submarines and 11 2,900-ton-displacement Soryu-class boats, the most recent — and the first with lithium-ion batteries — being commissioned into service in March 2020. A 12th member of the Soryu class, named Toryu, is undergoing tests before formally joining the fleet.

The Japan Maritime Self-Defense Force Oyashio-class submarine Mocishio during the Rim of the Pacific 2010 exercise north of Hawaii. , U.S. NAVY/CHRISTOPHER MCCORD

Beyond this 22-boat submarine fleet, Japan plans to add at least another two Taigei-class submarines, one of which was included in the defense ministry’s latest budget request.

It’s all part of a military spending program that encompasses big-ticket items ranging from the F-35 Joint Strike Fighter to hypersonic missiles. Japan’s Ministry of Defense has requested an annual budget increase for the last eight years now, reaching $55 billion for the next fiscal year, starting in April 2021.

As well as spearheading a maritime force that should help secure critical sea lanes in the East China Sea and the South China Sea, there’s a possibility Japan’s new class of submarines might also attract foreign interest. An offer of the previous Soryu-class boats to Australia was unsuccessful, but Tokyo has reshaped its national defense policy to include major arms exports. With an established lead in lithium-ion battery technology, the Taigei class, or its subsystems, could prove attractive. In the meantime, the propulsion concept is gaining traction elsewhere, including in South Korea.

Whether this type of battery propulsion finds a place on other navies’ submarines remains to be seen, but it’s clear that they are here to stay, with the JMSDF undersea force, at least, now well on its way to a lithium-ion-powered future.

Contact the author: thomas@thedrive.com