12v boat battery immersed in sea water...

[sarabande]

What happens to a 12v battery (either lead acid, or AGM) if the boat floods and sea water rises above the terminals ?

Looking to consider contingency responses. but need to know about gasses (?chlorine) , electrolysis producing hydrogen, big sparky stuff, etc.

Imaginative scenarios please

 

[Bru]

It explodes in a massive fireball and everybody within a hundred yards dies a horrible death

(Well, you did ask for an imaginative scenario!)

 

[sarabande]

nice one, Bru

 

[earlybird]

What happens to a 12v battery (either lead acid, or AGM) if the boat floods and sea water rises above the terminals ?
Looking to consider contingency responses. but need to know about gasses (?chlorine) , electrolysis producing hydrogen, big sparky stuff, etc.
Imaginative scenarios please

When I kept a boat in a drying estuary, over several years at least 2 boats sank at their mooring and several cars were submerged on the sands. I don't remember anything dramatic happening regarding their batteries except they were probably ruined. Wouldn't any small quantity of chlorine largely be dissolved in the seawater?
Should perhaps add that during these events, any occupant wasn't staying inside!

 

[jeanpaulcopie]

What happens to a 12v battery (either lead acid, or AGM) if the boat floods and sea water rises above the terminals ?

Looking to consider contingency responses. but need to know about gasses (?chlorine) , electrolysis producing hydrogen, big sparky stuff, etc.

Imaginative scenarios please

The worst is environmental pollution....

 

[VicS]

What happens to a 12v battery (either lead acid, or AGM) if the boat floods and sea water rises above the terminals ?

Looking to consider contingency responses. but need to know about gasses (?chlorine) , electrolysis producing hydrogen, big sparky stuff, etc.

Imaginative scenarios please

Chlorine produced at the + terminal/ connected wiring and severe corrosion. pH will fall .

Hydrogen produced at the - terminal. pH will rise

 

[lw395]

If you have large areas of + and - bare wiring or buss bar immersed and close together, you could get a lot of current flowing, heating etc etc.
If the seawater mixes with the acid, AIUI, ruined battery and signicant release of chlorine? I think this is only a real issue in half-flooded submarines TBH?

 

[VicS]

If you have large areas of + and - bare wiring or buss bar immersed and close together, you could get a lot of current flowing, heating etc etc.
If the seawater mixes with the acid, AIUI, ruined battery and signicant release of chlorine? I think this is only a real issue in half-flooded submarines TBH?

Simply mixing acid with seawater won't produce chlorine.

Getting seawater into batteries is another matter. Apart from chlorine we have also been told by Plevier that stibine, SbH₃, can be produced.

 

[lw395]

Simply mixing acid with seawater won't produce chlorine.

Getting seawater into batteries is another matter. Apart from chlorine we have also been told by Plevier that stibine, SbH₃, can be produced.

The chlorine thing seems to recur in submarine mythology.
Interesting point about antimony and stibine.
Of course adding any water to concentrated strong acid is potentially explosively messy.

In reality, I have seen batteries get immersed in open boats with no obvious ill effect.

 

[skipmac]

The answer of course depends on whether it happens in Hollywood or if it happens in the rest of the world. If it happens in Hollywood see post #2. If it happens in the rest of the world then on a practical basis, not much at least nothing dramatic or exciting in the least. Unless they're sealed then salt water in the cells will ruin the batteries, any batteries will discharge rather quickly through the salt water but not explosively. Battery acid will leak into the boat and if not diluted by water flow will corrode whatever it contacts.

Of course all sorts of other things will happen in the boat in addition to the battery thing, Wiring will be saturated with salt water and probably all need replacing. Bulkheads and any plywood structure will be wet and probably start delaminating, etc, etc, etc,

 

[Deleted member 36384]

... In reality, I have seen batteries get immersed in open boats with no obvious ill effect.

I think there are a couple of comments in some 'Total Loss' stories of electrics being powered up after complete submersion of the batteries. There are also more than a few stories in the same book where flooding and covering the batteries has not resulted in anything dramatic.

 

[Plevier]

The chlorine thing seems to recur in submarine mythology.
Interesting point about antimony and stibine.
Of course adding any water to concentrated strong acid is potentially explosively messy.

In reality, I have seen batteries get immersed in open boats with no obvious ill effect.

Stibine is not mythology, but it will only happen if the battery is charged, not if it's disconnected. Of course most batteries now are lead calcium. No antimony means no stibine.
Salt will ruin a conventional battery though.
An AGM should suffer no ill effects - in theory.

 

[Tammany]

This happened on mine after a partial seacock failure. Seawater over the level of the batteries, still worked & started the engine perfectly fine though lol. Their seemed to be a cloudy substance in the water and yes a real strong smell of chlorine gas. Took battery out and charged it in the garden and it seemed fine but replaced both of them anyways.

 

[oldbilbo]

The OP's question arose in the context of hull-breach or downflooding sufficient to cover a sailboat's batteries contained in an under-berth locker space. The wider idea being discussed ( privately ) was the prospect of making said sailboat 'unsinkable' by means of inflatable bags secured - when needed - to the floors bearers, as in..

There are those who consider that trying to survive in a part-flooded, but still floating, sailboat hull - with all the gear and resources still to hand - is likely to be a better option than trying to survive in a part-flooded, but still-floating liferaft. Especially in wild and windy seas far offshore.....

Those who have spent any time in liferafts will be nodding their heads sagely.

There are plenty of 'red herrings' such as risk of fire, etc. suitable for a wider debate, but this specific discussion was and should remain concerned with the effects on a breathable atmosphere of immersion of the batteries. My 'entering argument' was sealed AGM batteries and all exposed connections covered in the likes of Vaseline or other protective sealant, and I can see no realistic risk of asphyxiation from poison gas production. Hypothermia is a rather more real issue, in such circumstances.

Do the 'ayes' have it?

 

[sarabande]

I think we have advanced the forum's knowledge of what happens if you immerse a battery in sea water. Not very much, unless you are unlucky and happen to be near the battery when it is initially flooded.


One suggestion arising out of our exploration of the potential problem is to have a small, but high efficiency, battery (perhaps an AGM motor cycle battery ?) mounted and isolated well above the water line. With prepared connectors, it would then be possible to run VHF and e.g. a strobe. OK, it's long shot stuff, but when planning for survival, surviving the plan is important.

 

[Bru]

One suggestion arising out of our exploration of the potential problem is to have a small, but high efficiency, battery (perhaps an AGM motor cycle battery ?) mounted and isolated well above the water line. With prepared connectors, it would then be possible to run VHF and e.g. a strobe. OK, it's long shot stuff, but when planning for survival, surviving the plan is important.

Funnily enough, one item on my winter "to do" list (winter 'cos I have time then to sit, cogitate and tinker) is to work out a good scheme for doing just that. Keeping the battery in tip top condition being the bit I need to think about (can't just fit and forget 'cos of self discharge and simply manually connecting to a charger periodically is far too simple!)

 

[BobPrell]

One suggestion .... is to have a small, but high efficiency, battery (perhaps an AGM motor cycle battery ?) mounted and isolated well above the water line. With prepared connectors, it would then be possible to run VHF and e.g. a strobe. OK, it's long shot stuff, but when planning for survival, surviving the plan is important.

How about having the battery in a box which is closed at the top, not the bottom. Water cant get in, same as upside down bucket.

As requested, imagination.

 

[lw395]

I think we have advanced the forum's knowledge of what happens if you immerse a battery in sea water. Not very much, unless you are unlucky and happen to be near the battery when it is initially flooded.


One suggestion arising out of our exploration of the potential problem is to have a small, but high efficiency, battery (perhaps an AGM motor cycle battery ?) mounted and isolated well above the water line. With prepared connectors, it would then be possible to run VHF and e.g. a strobe. OK, it's long shot stuff, but when planning for survival, surviving the plan is important.

My first yacht had that.
It also ran the GPS, to prevent the GPS dropping out during engine starts.

 

[pmagowan]

Now we understand the scenario. I have thought about this topic quite a lot because I wonder why things are not designed, especially in blue water cruisers, to survive knockdown or capsize. I have, for a long time, becaome suspicious of the value of liferafts and I believe that they are a throwback to Titanic type vessels and can be dangerous in the context of cruisers, as demonstrated in the Fastnet 79 race. I had a landrover which was modified to be able to drive through deep water. I don't understand why a boat, Which lives in water, can not be designed to cope in most situations. First, keep the water out, but if it gets in then why can you not have the batteries in a sealed compartment with 'snorkel' style ventilation, same for the engine. This way, when the worst happens, you will still have a working engine and electrical system. It is not that difficult to make your electrical connections relatively safe from water and wires can be lead high but the batteries with their weight are best kept low. I don't think there is much risk from the batteries getting immersed themselves other than you lose electrical power which could be important when you have some flooding. Bilge pumps and lights spring to mind as useful.

 

[oldbilbo]

I wonder why things are not designed, especially in blue water cruisers, to survive knockdown or capsize. .... I don't understand why a boat, Which lives in water, can not be designed to cope in most situations. First, keep the water out....

Now you're talking..... and thinking about the many unchallenged 'givens' in boating, or because 'It's the rules' or 'Everyone else does....'

F'r example, while helping out recently with scrutineering the Multi50s at the Transat - a race for singlehanded pros - I noticed the checklist required inter alia a PAIR of horseshoe lifebuoys, each marked with the boat's name. No-one I asked - and certainly none of the skippers - had any idea of the circumstances in which it was envisaged these devices might be used. "Eet eez zee Rules"....

At the same time, it emerged that a previous requirement for Red Rocket Flares had been rescinded. They were no longer Required in the Rules. No-one knew why. Each of the boats had them on board from the previous year's events; most of them retained the flares 'cos they were seen as probably the most useful, in the likely circumstances.

I'm of the view we should question the norms, like posters above, certainly until we get convincing answers.