Possible Arrangement of Lithium-ion Batteries in Japanese Submarines

Diagram of possible shape of a Lithium-ion Battery (LIB) for a Japanese submarine. Note its 8 cells are in blue. This is from a January 2017 article on wispywood2344’s blog, http://blog.livedoor.jp/wispywood2344/archives/2017-01.html .

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Submarine Matters makes a feature of charting the development of Lithium-ion Batteries (LIBs), and other technologies, in Japanese submarines. The Japanese Navy (JMSDF) is very likely to be the first navy that will openly and operationally use LIBs. This will first be in Japan's first Soryu Mark 2 submarine (known as 27SS, Build no. 8126, Pennant no. SS-511) see SORYU TABLE. 27SS might be commissioned in 2019-2020 or later.

If Japan successfully uses LIBs for years, with few problems, Japan’s Western submarine competitors (Germany’s TKMS, Sweden’s SAAB-Kockums and France’s DCNS) may also develop LIBs for use from the late 2020s.

As Australia’s future DCNS Shortfins will have an almost completely new electrical system (along with most of its other internal fittings) the Shortfin might be one of the first diesel-electric (conventional) submarines to be built around LIBs. Australia therefore could rely on LIBs to provide extended, fully submerged, range. In support of this contention is the fact Australia never publicly expressed interest in AIP for its future submarines under the SEA 1000 selection process.

Japanese testing of LIBs technology may have occurred on one, two or all three Harushio class submarines that were converted to trainings submarines and then perhaps propulsion testbeds. Those three submarines were renumbered TSS-3606, TSS-3607 and TSS-3601 (see Harushio “Vessels” Table). It is even more likely that Oyashio class TSS-3608 was partly converted to a LIBs testbed.

Comments made anonymously, 21-28 January 2017 indicate that LIB arrangements are very difficult to know with any certainty:

From the published information available it is difficult to work out how old Lead-acid Batteries (LABs) were moved around in a submarine. LIB moving arrangements are even more difficult to guess.

Suggested Model

The arrangement of LIBs in a future Japanese submarine is aimed at promoting safety and efficiency. The heavy LIBs module (weighing 770kg) shown in the diagram above must be securely anchored on a pedestal. This anchoring may take place as follows.

-  First, a battery module consisted of 8 single cells (see diagram), where the bottom two positions
    are empty, is placed on the pedestal.

-  Next, the battery module is anchored to the pedestal by bolts using the bottom empty positions.

   After anchoring a battery module, 2 single cells are fixed in the bottom two positions. That is why

   the bottom two cells seem to be convertible spaces.

-  Further provision for anchoring may be:
   =  more spacing outside the modules, including an accessible central aisle on the keel
   =  the LIBs' front facing the aisle, and
   =  a 6 by 6 row of LIBs arranged in clusters on each side of the aisle.

Perceptions Supporting Model 

In support of the above anchoring model is Japanese Industrial Standard (JIS) For LIBs Installation In Surface Ships. One of the requirements for installation is ”battery systems shall be anchored to robust structural elements of the ship by bolts and nuts.”

Also significant are pictures of prototype LIBs of the Japanese Navy (JMSDF) which clearly need a firm installation process. But any positions/holes for bolting outside of the battery module are not apparent. This strongly suggests bolting is conducted inside and at the base of the battery module. Adequate space for bolting is needed - then two single cells can be placed at the bottom of the module.

Batteries on pedestals have the downsides of a higher center of gravity (maybe increasing vibration and top-heaviness) and may expand any stray magnetic field. But mounting LIBs on pedestals has the benefits of providing better access for installation, maintenance and removal.

One should qualify the above comments on LIB arrangements. The comments are reliant on published sources and Japan’s first fully LIB submarine (27SS, see SORYU TABLE) hasn’t even been completed yet.

What Is Known About Old LAB Arrangements Offers Little Help

Looking at a reference of LAB arrangements on old Oberon submarines suggests ambiguity about how batteries are placed or removed. This may or may not take place using both vertical and horizontal hydraulic jacks [1]. Then, there is no the pedestal for LABs. Also battery modules for LABs are arranged in a fully closed packing manner. Whether LIBs use the same arrangement is an unknown.

[1] old Canadian C.F.’O’ CLASS SUBMARINES (TRAINING NOTEBOOK ELECTRICAL) provides detailed information on LABs in Oberon class (aka "O boats") subs, used by Canada, Australia and, of course the UK (designer and builder) etc, see: http://jproc.ca/rrp/rrp2/oberon_battery_and_electrical.pdf [about 5 MB] In particular see Page 11.26. Where it states: “C. Cell Lifiting Gear: Sick [that’s what it says!] cells are removed from batteries by cell lifting gear . Each submarine carries its own lifting gear.” also see:

-  Page 11.2 (Fig.11.01 Battery compartment – typical arrangement) and

-  Page 11.16 (Fig.11.06 Arrangement of cell group water cooling connections)

What We Can Conclude About Japan’s New Submarine LIB Arrangements From 2020 Onwards

First, it has taken a long time to develop LIBs and great deal of effort toward establishment of their safety and reliability. A modern quality control system, utilising a theoretical approach, assisted by computer simulations, provides guidance on any potential for battery failure and helps predict average battery life. But, these theoretical results still need validation through practical use and experimentation, which takes time.

Second, converting a battery system, from traditional LABs (used for up to 120 years by submarine countries) to LIBs, is a difficult process. This replacement process includes:

-  elimination of LABs’ safety ventilation system and water cooling system,

-  total conversion of electrical system (including totally new wiring, switches and

   battery/electrical control computers, etc)

-  installation of the LIBs' safety gas cylinder and piping for fire extinguishing system, and

-  as a submarine's batteries in total weigh hundreds of tons re-balancing the whole submarine is
   necessary, partly achieved by rearranging some fuel and buoyancy tanks. 

So, it is preferable to build a new submarine design (like the DCNS (future) Shortfin) around LIBs rather than retrofitting LIBs in a LABs submarine.

By Anonymous sources and Pete