Japanese Approaches That Reduce Hazards of Submarine Lithium-ion Battery Use

Japan's main submarine battery producer, GS Yuasa, does not advertise the secret Lithium-ion Batteries (LIBs) for its new class of Soryu submarines (the Soryu Mark 2s designated 27SS and 28SS). But a budding mole (probably already working for China) would find such LIBs in GS Yuasa's Large "Industrial and Military" (LIM) production division. Above is one of Japan's manned civilian submarines, the "SHINKAI 6500 Deep Submergence Research Vehicle" which, powered by GS Yuasa LIBs (driving a motor) can dive to 6,500 meters.

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The safety of a submarine Lithium-ion Batteries (LIBs) system is essential, just like all systems on a submarine. Submarines, even in peacetime, are full of systems inherently dangerous to crews. Safety for LIBs is even more essential because:

i)   LIBs are a new technology for submarine compared to Lead-acid Batteries (LABs). LABs have been used since at least the 1880s (135 years ago). LIBs have never been used operationally.

ii)  the high energy density of LIBs (compared to LABs) makes them more prone to fire if their 

     design, management and monitoring systems are deficient or faulty.

Drawing on comments from Lithium-ion Battery (LIB) safety experts mid to late October 2016.

In Japanese LIBs for submarines, the manufacturer of even a single cell or battery has to satisfy:

i)    safety management system requirements and

ii)   product requirements.

Only a few Japanese manufacturers can conduct risk assessments and reduction measures for whole systems through a submarine's entire operational life. Satisfaction of all LIBs for submarine requirements needs detailed knowledge and comprehensive prior experience of providing LABs for submarine. This likely makes GS YUASA the appropriate LIBs manufacturer in Japan.

The LIBs process requires intensive identification of risks/hazards at all stages: production process, battery assembly, installation on the submarine, operation (see [1] below) on the submarine, removal from the sub and disposal of LIBs.

Analysis of hazard source, risk assessment and risk reduction are as follows:

i)    Modelling, Testing and Observation to identify and remove potential hazards and/or hazardous

       practices - such as recharging after over-discharging, Electromagnetic compatibility (EMC),

       shock resistance, etc - should be carried out,

ii)   risk should be assessed based on magnitude of effect and probability of hazard source, and

iii)  the performance targets of safety standards should be established and activities of risk reduction

       should be conducted.

In the above process the following approaches should include: Fault Tree Analysis, Failure Mode and Effects Analysis, and Safety Integrity Levels.

As an example of a Japanese standard on “secondary” lithium cells and batteries for a ship’s-electrical energy storage equipment is JIS (Japan Industrial Standard) C 8715-2 Secondary lithium cells and batteries for use in industrial applications-Part 2:Tests and requirements of safety Appendix E Establishment of target of safety level and risk reduction.

Secondary batteries (secondary cells or rechargeable batteries) must be charged first, before initial use, discharged into a load, and are typically recharged many times. LABs, LIBs and LSBs (described in a future article) are secondary batteries.

[1] HOW LIBS FUNCTION SAFELY WHEN ACTUALLY OPERATING IN THE SUB

Unsurprisingly Submarine Matters is particularly interested in how LIBs function safely when actually operating in the sub. The LIBs safety experts advise:

i)    LIBs should be operated within a specified temperature range (10C - 45C).

ii)   For lower temperature operation (under 10C) adequate measures, such as environment controls

       should be taken into account at the design stage to prevent thermal runaway caused by a 

       build-up of metallic lithium deposits.

iii)  A ventilation system, fire detector and a fixed fire extinguisher system should be fitted in the

       submarine. Carbon dioxide or nitrogen gas should be used as the extinguishing agent. Fresh

       water and/or sea water should not be used. Carbon dioxide is probably used instead of nitrogen,

       because carbon dioxide is heavier than air and nitrogen is lighter.

iv)   There should be highly detailed and complete understanding of effects on an operating sub’s:

        -  inclination in an aft/fore direction, port/starboard and at diagonal directions (noting the
           X-plane rudders) 

        -  vibration, and

        -  temperature effects on the electrochemical properties of LIBs (such as current-voltage, capacity-voltage, charge-discharge relationships and aging).

v)     As the above mentioned safety system of LIBs is quite different from that of LABs, thorough

        experimental then practical trials of the LIBs on the first two LIBs-only Soryus (27SS and 

        28SS) is very important. Simultaneously, a great many supplementary laboratory tests including

        "stress tested to destruction by fire" should be conducted. 

GENERAL BACKGROUND ON LITHIUM-ION BATTERIES (LIBS)

The Japanese Government and private industry have been methodically analysing the performance of Lithium-ion Batteries (LIBs) intended for use in submarines for more than a decade. Japan has actually been mounting LIBs during that time into older now-non-operational submarines designated "training" or more revealingly "testbed". LIBs may be the technology area that Japan has the greatest lead over its French (DCNS) and German (TKMS-HDW) competitors.

It appears that recent performance data on LIBs for submarine are kept very confidential by all 3 countries - on Commercial-in-Confidence and National Security grounds. This makes it very difficult to ascertain whether any of the 3 have superior or mature (for use on operational subs now) LIBs.

The US is also be developing LIBs for very small (ie. less than 30 tonnes) battery only Special Forces/SEALS Submarines. It is unknown whether the US Government (and US private industry) would exchange more LIB technical information with the US’s Pacific ally, Japan, or its NATO allies, Germany and France.

It is possible the Japanese Government (or companies) may share some LIBs technology with the US Government/Navy/companies under secret deals.

Please connect with Japan's Lithium-ion Battery Advantage..., October 15, 2015.

Authors:
-  The LIB safety experts - who did most of the research and most translation.

-  Pete and Local Helpers - some research and translation, the General Background.