Choice of Submarine LIBs - Management and Operation

In Submarine Matters' ongoing examination of Lithium-ion Batteries (LIBs) Anonymous's research and comments are always helpful. Anonymous's comments of  September 16 to 27, 2017 reveal much about the likely choice, management and operation of LIBs on submarines. Japan is leading the way with LIBs - planning full conversion to LIBs on new submarines launched from 2018 onwards (see Table below).

In the development of new LIB materials and control equipment for Japan's latest Soryu submarines, rigorous testing, prior to operational use, is required. LIB materials and equipment may fail under accelerated and severe condition testing. This includes testing under:

-  high or very low temperatures (the operational temperature of LIBs on Japanese submarines is
   within the range of 10-45 degrees C for efficient and safe operation) 

-  high pressures

-  strong mechanical stress, and

-  continuous vibration testing, etc.

Tri-ring advised the two simplest ways to avoid the particular LIB problem of "lithium plating" is to:

-   prevent over voltage during charging of LIBs (above 4.2 volts per cell), and

-   charging and discharging at low temperature (below 15⁰C). 

He adds that to counter thermal runaway of LIBs, great advances have been made in material science. One of them is a ceramic separator that has much higher resistance against heat.

The Japanese Ministry of Defence's (MOD) Acquisition, Technology & Logistic Agency (ATLA) and the Japanese Navy have been (and will be) conducting such testing of LIBs. For more accurate establishment of LIB safety standards, non accelerated testing under normal condition is preferable, even if this is time-consuming. 

Choice of LIBs

Japan has explored submarine use of many LIB combinations, including two that show exceptional stability at low temperatures and long charge-discharge cycle lives. These are : 

-  Lithium Iron Phosphate (LFP) 2,000 cycle lives. As indicated here Anonymous advises the next
   subclass of TKMS Type 212As may adopt LFP (Pete would say the new 212As would be launched
   during the 2020s) 

-  Lithium Titanate (LTO) ( Li₄Ti₅O₁₂ ) 7,000 cycles, made by Toshiba. 

For LFP and LTO such stability at low temperatures and with long cycle lives comes at the cost of  relatively low energy density.

-  Lithium nickel cobalt aluminium oxide (NCA) Drawing from this article. To remedy this low LIB
   energy density problem Japan may well have settled on NCA ( LiNiCoAlO₂ ) LIBs for its Navy.
   These LIBs are made by GS Yuasa. Such LIBs are ideal for the Japanese Navy's mid-range
   continuous patrol operations.

All this LIB testing and subsequent use on Soryu submarines via liaison with France's Naval Group may contribute to use of LIBs on Australia's Shortfin Future Submarines (FSM). LIBs on Shortfins may be added from the first Shortfins onwards or fitted to later build Shortfins. TKMS, Saab-Kockums, Naval Group, Russia, China and MHI/KHI may develop fundamentally different LIBs for other submarines. Also their differing diesel engines are an additional diesel-electric variable. This means the efficiency and safety of LIBs developed by one submarine builder may note ensure efficient and safe use by other builders. 

For example Saab-Kockums and Russia that build submarines mainly for cold water operations may prefer LFP LIBs that may be more efficient in icy temperatures. As a customer Canada may prefer low temperature LIBs for its near Arctic Ocean operations. 

LIBs Management and Operation

Anonymous does not think a submarine's LIBs are discharged homogeneously (all at once and evenly). The numbers of charges and discharges of  LIBs during (say) a total of 4 charge-discharge phases over 96 hours) might occur as follows:
i)  half of the LIBs in the forward battery section may be used for the sub's first fully submerged dive and then charged in the first snorting, 
ii)  the other half of the forward LIBs is used for the second dive, then charged in the second snorting phase 
iii)  half of the LIBs in aft battery section is used for the third dive and then charged in the third snorting, and
iv)  the another half of the LIBs in the aft battery section is used for the fourth dive and then charged in the fourth snorting.

The management/operation (M/O) system of batteries/propulsion of  Japanese Oyashio and Soryu submarines is shown in 1 to 3 below. 

1 Oyashio class (built 1994-2006, see Table below)
In the eleven Oyashio class subs are classic DC motors reliant on limited capacity LABs. These make  the sub's fully submerged speed control complex. LABs are in 2 identical sections fore and aft (ie. 4 identical sections overall)
M/O of LABs are in parallel or series connection in sections/subsections
Propulsion: 2 identical DC motors

2 Soryu MK 1's (built 2005-present)
In the ten Soryu Mk 1s, latest Permanent Magnet Synchronous Motors (PMSMs) make speed control of the submarine easier. But the management of two power supply systems (LABs & AIP) is complex.
LABs: fore and aft sections consisted of 2 identical subsections, respectively (ie. 4 identical sections overall)
Stirling AIP
M/O of LABs: unknown
Propulsion: smaller and bigger AC motors; smaller one is for low speed

3 Soryu Mk 2s (estimation)(built 2015 (see Table) perhaps through to 2018)
Soryu Mk 2s adopt the simplest M/O system among Japanese submarines.
LIBs: fore and aft sections will consist of 2 identical subsections, respectively (ie. 4 identical sections overall)
M/O of LIBs: unknown, but may be in 4 phases, see i) to iv) above.
Propulsion: 2 identical AC motors

 TABLE - SORYU & Oyashio Program as at October 3, 2017 

SS No.	Build No Name	Pennant No.	MoF approved amount ¥ Billions FY	LABs, LIBs, AIP	Laid Down	Laun -ched	Commi ssioned	Built By
5SS Oyashio	8105 Oyashio	SS-590/ TS3608	¥52.2B FY1993	LABs only	Jan 1994	Oct 1996	Mar 1998	KHI
6SS-15SS Oyashios 10 subs	8106 -8115 various	SS-591-600	¥52.2B per sub FY1994-FY2003	LABs only	15SS Feb 2004	15SS Nov 2006	15SS Mar 2008	MHI & KHI
16SS Soryu Mk 1	8116 Sōryū	SS-501	¥60B FY2004	LABs + AIP	Mar 2005	Dec 2007	Mar 2009	MHI
17SS	8117 Unryū	SS-502	¥58.7B FY2005	LABs + AIP	Mar 2006	Oct 2008	Mar 2010	KHI
18SS	8118 Hakuryū	SS-503	¥56.2 FY2006	LABs + AIP	Feb 2007	Oct 2009	Mar 2011	MHI
19SS	8119 Kenryū	SS-504	¥53B FY2007	LABs + AIP	Mar 2008	Nov 2010	Mar 2012	KHI
20SS	8120 Zuiryū	SS-505	¥51B FY2008	LABs + AIP	Mar 2009	Oct 2011	Mar 2013	MHI
No 21SS			No 21SS built
22SS	8121 Kokuryū	SS-506	¥52.8B FY2010	LABs + AIP	Jan 2011	Oct 2013	Mar 2015	KHI
23SS	8122 Jinryu	SS-507	¥54.6B FY2011	LABs + AIP	Feb 2012	Oct 2014	7 Mar 2016	MHI
24SS	8123 Sekiryū	SS-508	¥54.7B FY2012	LABs + AIP	15 Mar 2013	2 Nov 2015	13 Mar 2017	KHI
25SS	8124 Seiryū	SS-509	¥53.1B FY2013	LABs + AIP	22 Oct 2013	12 Oct   2016	Mar? 2018	MHI
26SS	8125	SS-510	¥51.7B FY2014	LABs + AIP	2014	?	Mar 2019?	KHI
27SS First Soryu Mk 2	8126	SS-511	¥64.4B FY2015	LIBs only	2015	2017?	Mar 2020	MHI
28SS  Second Soryu Mark 2	8127	SS-512	¥63.6B FY2016	LIBs only	2016?	2018?	Mar 2021?	KHI
29SS First Soryu Mk 3	8128	?	¥76B FY2017	LIBs only	?	?	2023?	MHI?
30SS Second Soryu Mk 3	8029?	?	¥71.5B FY2018	LIBs only	?	?	2024?	KHI?

Table from information exclusively provided to Submarine Matters. LABs = lead-acid batteries, AIP = air independent propulsion, LIBs = lithium-ion batteries. ¥***B = Billion Yen. MHI = Mitsubishi Heavy Industries, KHI = Kawasaki Shipbuilding Corporation of Kawasaki Heavy Industries.

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So LIB Management and Operation is complex but as the batteries work to computer terminals a submarine's engineers should be able to manage and operate LIBs more easily than lead-acid batteries.

By Anonymous & Pete