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I have always wondered why the diesel electric submarine industry has not kept pace with the consumer market for high power/energy density batteries. We have seen a historical transition from lead acid, to nickel-metal hydride, to lithium ion batteries in the EV market.

With a few exceptions, like the last bunch of the Soryu class which have implemented lithium ion battery technology, most modern high tech diesel electric submarines still rely on lead acid batteries.

I have heard many arguments on this topic, but have found none of them to be particularly persuasive. These include:

A) Specific energy isn’t so important for submarine batteries since ballast is needed

Counter: This doesn’t account for space, which is vitally important, and lead acid batteries have relatively poor energy density.

B) Lithium ion is too hazardous; safety is important on a submarine

Counter: What about other battery technologies? What about nickel metal hydride batteries which exhibit double the energy density of lead acid batteries and are as safe as lead acid batteries?

C) Lead acid batteries are reliable and give high specific power

Counter: Nickel cadmium and nickel metal hydride are just as reliable in terms of charge cycle duration, and the latter has even greater specific power capability.

D) There’s an issue of cost

Counter: Yes lead acid technology is particularly cheap. But this doesn’t account for the high end diesel electrics (e.g. Type 212) which use expensive fuel cell technology along with modern electronics. It’s hard to believe that cost could be an issue considering that lithium ion is even more expensive than the alternatives listed, and is nevertheless (finally) being adopted in rare cases.

So what gives? Why was there and still is a battery technology lag in the diesel electric submarine industry? Especially since underwater endurance is one of the most important characteristics of such submarines.

Alex Popescu
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  • What is the cycle life between lead acid, NiMh, and NiCd? I imagine NiCd would not fare so well with memory and all. And how much energy can you pump into each chemistry per weight? If your NiMh are twice as energy dense then you can charge at the same power levels as before as long as NiMh has a charge rate of 50% your old chemistry or better. But if it's less then you ultimately can't pump as much power into the batteries as before. – DKNguyen Aug 31 '21 at 04:58
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    Presumably because the design criteria makes them superior. I was a submarine officer, but we didn't have the specs for ship design. My guess is it's a combination of performance, service life, and the need for ballast anyway. – Tiger Guy Aug 31 '21 at 15:05
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  • Lead-acid batteries require less sophisticated control. 2) Relatively more tolerant to charging/discharging (deep) and loading. 3) So, easy of maintenance/troubleshoot would be an important factor.
    • – jay Aug 31 '21 at 15:43
  • From EE: Why are lead-acid batteries preferable for submarines? – StainlessSteelRat Aug 31 '21 at 18:15
  • @StainlessSteelRat: Thanks for the link. I found much of those answers in the link unsatisfying and really they just paralleled the same stuff I addressed in my post. The answers were similar to the stuff I've encountered before, examples like "we need ballast and therefore weight is not important"; okay but what about space and energy density? There were also safety and reliability concerns brought up as answers,. which I already addressed. Thanks. – Alex Popescu Aug 31 '21 at 22:13
  • @jay: You bring up a good point. There's no doubt that batteries like NiMh are more complex and therefore harder to maintain and troubleshoot. But then we would have to believe that submarine makers are willing to give up twice the underwater endurance (NiMh has twice the energy density) in favor of maintainability. That doesn't seem plausible to me, because modern & advanced submarines such as the Type 212 use highly complex systems like hydrogen fuel cell technology. So they are clearly willing to give up maintainability in favor of performance, and yet they have stuck with lead acid. – Alex Popescu Aug 31 '21 at 22:19
  • Li are scary because warships must survive hits with explosives. NiMH and NiCd suffer from higher self discharge, although this has supposedly been fixed in recent generation tech. – Pete W Sep 01 '21 at 00:36
  • You're going to encase all of them in steel plate anyway. So the power and energy density of the actual item as built shows much lower gains than it would with less protected batteries. The actual specific gravity of a wet lead installation is only about 2.25. So the ballast argument isn't great. My cousin's Christmas cake is denser than that. Accidentally shorting a string of wet lead sub batteries gets you about a million amps and a emp driven by an amp rise of about 100,000,000 per second, that's a lot but it won't break the sub. – Phil Sweet Dec 30 '23 at 03:59
  • Bolt a Lion to ground and you have a real emp event on your hands. It can blow squibs in the missile tubes or set torpedoes off. Wet lead is self regulating at a level you can work with and protect against because we have about 100 years practice by now. – Phil Sweet Dec 30 '23 at 03:59
  • And fires. Submariners really hate fires. – Phil Sweet Dec 30 '23 at 04:01
  • @PhilSweet You'd think it would be a nice change of pace being surrounded by all that water all the time, but I guess not. – DKNguyen Jan 03 '24 at 22:42