SS-501 Soryu - Lithium-ion Batteries

The latest Oryu diesel-electric attack submarine was handed over to the Japanese Navy on 05 March 2020. The ceremony, according to Kyodo news agency, was held in the city of Kobe at the shipyard of the Mitsubishi Heavy Industries Corporation, where this submarine with a displacement of 2950 tons was built. The 84-meter "Oryu" is armed with six torpedo tubes, through which ship-to-ship class Harpoon missiles can also be launched. Her team consists of 65 people. About 66 billion yen (more than $ 611 million) was spent on the construction of the submarine.

This is already the 11th attack heavy submarine of the Soryu class, which experts consider to be one of the best in the world. By the duration of their continuous stay under water, they approach atomic submarines and are distinguished by considerable noiselessness. The Oryu is the first one equipped with the latest lithium-ion batteries, which will allow it to operate even longer when immersed. Under water, a submarine can move at a speed of up to 37 km per hour. In Japan, 22 submarines, including training ones, were currently in service. Next spring, the country's Navy will receive another Soryu-class submarine.

A military submarine can be very expensive to build. For example, it can cost about $750M for an SSK-class submarine and over $2 B for an SSN-class submarine, and it can take about two years to build. Such military submarines generally have about 60 to 100 crew members to operate in three shifts.

While underwater, a submarine has a limited air supply for the engine and the crew members. Therefore, the UV has to surface to get air for the engine, to charge up the battery (e.g., for SSK-class submarines), and to pressurize air into storage for the crew. Similar to the buoyancy control equipment, the air storage apparatus needs pneumatic valve control monitoring and maintenance. While on the surface on the ocean, the UV can be in a vulnerable position during the combat mode.

The so called "Super Soryu" class of submarines was intended to fulfill Australia's requirement for a new advanced attack submarine. It would have used lithium-ion batteries instead of AIP and many thought it was a favorite to win the tender.

GS Yuasa, the Kyoto-based developer and manufacturer of battery systems, said in a 21 February 2017 press statement that lithium-ion batteries will be mounted on two Soryu-class boats currently in build for the Japan Maritime Self-Defense Force (JMSDF). The first such boat will be commissioned in March 2020.

On 09 October 2018 the Japanese corporation Mitsubishi Heavy Industries launched the Soryu-type diesel-electric submarine Oryu at the shipyard in Kobe. The new submarine was the first Japanese ship of this type, equipped with lithium-ion batteries. Compared to previous submarines of the "Soryu" class, Oryu does not use lead-acid batteries, but lithium batteries, designed by GS Yuasa. It is said that these high performance batteries store twice the energy. In the near future, the ship would begin trials, and in March 2020 it would be transferred to the Japan Self-Defense Forces.

Diesel-electric submarines batteries are needed for covert movement under water, when starting diesel engines to power running electric motors is undesirable or completely impossible. Usually lead-acid batteries are used on submarines. They make the ship's structure heavier, cannot provide a long duration of travel, and charge for a long time.

Japanese designers decided to use lithium-ion batteries in a submarine for several reasons. First, batteries collected from such batteries have a significantly larger capacity than lead-acid ones. At low speeds, the submarine range on lithium-ion batteries is comparable to the range on lead-acid batteries and the Stirling engine. Secondly, at high speeds, the range of the ship exceeds this figure when using conventional batteries. Finally, thirdly, lithium-ion batteries can be recharged using higher currents than when charging lead-acid batteries. This means that it takes significantly less time to fully charge lithium-ion batteries.