Sub Propulsion Systems: LIBs, AIP, DRDO, FC2G, TKMS, IFEP

Over the last week, with the excitement of Canada choosing the TKMS Type 212CD and SubMatts reaching 10 million page views Shawn and Gessler made some very interesting comments that deserve revisiting, 

Because the comments are aimed at a dedicated submarine audience, with considerable assumed knowledge, the comments are frequently without explanation or expansion of all acronyms.

Two of the comments below articles were:

An interesting comment by Gessler of July 7, 2026

"Thanks for the great article [Indonesia starts Scorpene Evo production] Shawn!

It appears the Indonesians may have adopted the Japanese philosophy of Lithium-Ion Batteries (LIBs) being used to replace the AIP system, instead of supplementing it as on the German [TKMS] (and Indian) concepts of operation.

LIBs are particularly useful for high-speed bursts or any such relatively quick discharge of energy, which is something most traditional AIPs (including fuel-cell type) may not be capable of, to the same extent. Where the AIP excels however is in 'drip charging' the system, extending underwater endurance for increased on-station time and so on.

Using the two systems in conjunction (like on Type-212CD or India's upcoming P-75I) would create a lot of operational flexibility for diesel-electric submarines, but of course that comes at additional cost, weight (displacement) & complexity as compared to a LIB-only configuration. So there are several merits for going the LIB-only way unless the operating Navy has very specific requirements that call for a LIB + AIP setup.

In case Indonesia decides to 'upgrade' their Scorpene Evos during one of their scheduled refits a decade or so down the line, I wonder if they'd be interested in DRDO's Fuel-Cell AIP that India has developed for their own Scorpenes, provided the system is finally proven on an actual refitted Kalvari-class (Indian Scorpene) boat by that point. France's Fuel Cell 2nd Generation (FC2G) AIP system is also an option, though it too remains unproven on an actual submarine.

But I guess if Indonesia really wanted AIP, they'd have gone for it from the start. Oh well, who knows what the future holds.

Cheers Gessler"
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Shawn C replied July 8, 2026. "Hi Gessler! Apologies for the late response.

I took [Indonesian shipbuilder] PT PAL's president's claims as brand marketing and the usual "my next boat is better than your current boat" one-upmanship. Note that Singapore already has more submarines than Indonesia (4 in service, 1 working up, 1 fitting out).

I know TKMS has been conducting R&D on LIB batteries since 2014, and refitted a Type-212A in 2024 as a demonstrator - https://thedefensepost.com/2024/10/17/thyssenkrupp-battery-german-sub/

TKMS seems a few years behind the South Koreans and Japanese with LIB technology, but these batteries are supposed to be swappable "without design change" on the Type-209NG - https://www.tkmsgroup.com/submarines/submarine-classes/hdw-class-209

This implies that the Singaporean Invincible-class (Type-218SG) can switch to LIB when they come in for maintenance.

I have been curious of LIB use in military warship power generation for some years, especially as large cruise ships now use such systems to keep the lights on, example: https://corvusenergy.com/products/corvus-dolphin-nxtgen-ess-energy

Singapore's upcoming Victory-class MRCV will use IFEP with diesel power generation, but the use of LIB is not mentioned. LIB will act as a critical backup in damage control, for its ability to smooth out surges and keep high-energy critical systems, like AESA radar, powered."