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Comment by ilamont | Hacker News Reader

Fishermen sometimes happen upon submarine accidents. This one dates from 2003:

On April 25, 2003 the crew of a Chinese fishing boat noticed a strange sight—a periscope drifting listlessly above the surface of the water. The fishermen notified the People's Liberation Army Navy (PLAN) which promptly dispatched two vessels to investigate.

https://www.chieftain.com/story/news/2018/06/07/in-2003-chin...

Every one of the submariners died.

There was another reported Chinese sub accident in 2023, but it's not clear how it was discovered (https://www.rfa.org/english/news/china/china-submarine-death...).

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During world war two, German U-boats used to have issues with chlorine gas being produced from the batteries and it would flood the boat and kill everyone onboard.

My grandfather was in a US Navy salvage group in WWII. At the time, to verify an enemy vessel (especially subs) had been sunk, they would send down divers in the old fashioned "heavy gear" suits to identify the vessels.

They would also bring up proof, usually something that could be tied to the vessel, which could be a piece of military-grade equipment or even silverware engraved with the names of the ship or the enemy seal.

This is what the suits looked like:

https://en.wikipedia.org/wiki/Standard_diving_dress

Super cool

My grandfather was a submariner in the Pacific during the war, they were even inside Tokyo bay during wartime. He had many stories, one of them was that the batteries always got the priority in regards to water. Especially on patrol and missions, they would often go days between wiping themselves down with hand towels from a basin of shared water, all to preserve the fresh water for the batteries.

He was on the Saury

Excuse my ignorance, what did the batteries need fresh water for, cooling?

Lead acid batteries, especially very old ones, actually consume water. The electrolyte is sulphuric acid diluted in pure water. When the battery is charging, some of the water is electrolyzed into hydrogen and oxygen gas. Modern lead acid designs still have this flaw, but it's much reduced and you typically don't need to refill them. Look at the warning stickers on your car battery, it's talking about hydrogen gas.

To be more specific, that is why the battery needs to be in a place that can vent.

When I replaced the AGM battery on my German car, I learned that, even though they don't vent under normal conditions, still have a vent hole. But that's paired with a pressure regulator and not for normal conditions.

Which makes me wonder: did BMW start to use AGM so they can move the heavy battery to the trunk, which helps with weight balance? Or was it an emissions thing that enabled them to move it to the trunk.

I've always wondered why they put it there too.

> They would also bring up proof, usually something that could be tied to the vessel, which could be a piece of military-grade equipment or even silverware engraved with the names of the ship or the enemy seal.

I believe traditionally, a diver will bring up a ship's bell for this purpose, if they are able. But maybe I'm off base about about, particularly when it comes to an enemy ship.

https://en.wikipedia.org/wiki/Ship%27s_bell

https://qr.ae/p26Ha0

https://www.washingtonpost.com/history/2024/02/20/bell-ship-....

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