Battery acid and salt water

[chabrenas]

Many books and articles warn that allowing battery acid to come in contact with salt water will give off chlorine. My chemistry is very, very rusty, but I don't see why the chlorine ions shouldn't remain in solution. However, letting salt water get into a battery seems likely to result in chlorine being given off at one or other part of the charge/discharge cycle. Anyone here qualified to tell me the true story?

[mydauphin]

Interesting, that is something to that you will only know if you test it. It will probably generate portions of Sodium sulfate and hydrochloric acid. It will release some sulfur acid and a little chlorine gas. But it should not be violent and chlorine will be the least of your problems. Or it could just dilute acid and just generate some sodium sulfate. Also depends on temperature. Try it and let me know.

[chabrenas]

I think sodium sulphate is rather less soluble than the other salts obtainable from the mix, so I suppose some could precipitate out, causing chlorine to be given off to restore the balance.

It seems pointless to do my own experiments when someone who knows their chemistry well should be able to predict the result. Of course, sulphuric acid and salt water swilling around the cabin floor or the bilges is likely to encounter the occasional bits of copper, alloy, brass, alulinium, etc., in close enough proximity to form a cell that might increase the cahnces of producing chlorine gas.

[CDK]

Mydauphin is correct, the stronger acid makes a salt with the available sodium, the chlorine forms an acid with the freed hydrogen. But since seawater contains just 2-3% salt, the main effect is that the acid is diluted. If this happens inside a battery it is much more complicated because the lead becomes involved.
But it surely ruins the battery.

[chabrenas]

While they remain in solution, you can't talk about the ions pairing off as HCl and NaSO4, but some NaSO4 may precipitate out if it isn't a very soluble salt.

Ruining a battery is a repairable process, but humans can't inhale much chlorine and still remain repairable, so I'm trying to find out whether the chlorine story is a myth, or whether there are specific conditions in which it can be released.

It sounds to me as though spilling sulphuric acid into a wet battery box, or even into the bilges, is not going to release chlorine, but I have that niggling worry about what could happen if the (now somewhat diluted) mix surrounded a couple of dissimilar metals down there...

[mydauphin]

I think discussion is pointless, you shouldn't put seawater in batteries or breath the chlorine. That is why I use gel batteries and they are outside living space. Is there another reason for this discussion then may be we can go further.

[Fanie]

If a yacht overturn and battery acid is to mix with sea water your concern is not the small amount of chlorine, you may or may not even notice, but what is a concern is the battery acid is going to burn your skin ears and eyes and bugger almost everything els up it comes in contact with.

As mydauphin suggested, use SLA batteries. Worst that can happen with them is generating a bit of hydrogen before going flat if the situation isn't resolved, which sounds like the boat has sunk already.

There are different types of chlorine, some are more dangerous than others, a chemical expert should be able to explain the different types and where they are found, ie pool chlorine is different from chlorine you get when burning PVC.

A special combination you could try is mixing pool chlorine with brake flood. In about 5 mins you would be scattered all over the boat. So don't bleed the boat's brakes in the pool I say :D

[marshmat]

Having worked at pools a while back, I think it's safe to say that mixing pool chlorine with just about anything other than water is not a particularly smart move!

(Since we're on a chemistry binge: the unstabilized, granular variety is usually calcium hypochlorite, and public pools sometimes use sodium or lithium hypochlorite in solid or near-saturated-solution form. The "hockey pucks" used in backyard pools are most often stabilized trichloro-s-triazinetrione, or trichloroisocyanuric acid. Nobody uses pure gaseous anymore, for obvious reasons.)

I would have to actually sit down with an inorganic chemistry handbook and do the calculation to answer your question about chlorine release, chabrenas. I do know that chlorine gas is released if an electric current is passed through saltwater- I've smoked people out of a lab that way once, while testing an MHD pump. As to getting battery acid in the bilges- yup, that'll be very very bad for any equipment or fittings down there, as well as for any person who dares to enter.

[chabrenas]

When I say chlorine, I mean the gas Cl2, not bleaching and sterilising agents that release chlorine ions in solution.

I agree entirely with those who say use Gel or AGM batteries (they weren't available when I did most of my offshore racing), but looking around forums and sales pages suggests that the vast majority of boaters still use flooded cell lead-acid batteries, just as most of them use crappy cables and connectors.

I am writing a series of blog posts about marine electrics that I hope will prove useful, but it's no use just telling people what I think is good practice when it looks as if the vast majority if the boating world doesn't follow it - for various reasons, including a few old wives' tales. I need to debunk the rubbish and give good reasons for following best practice, even if it costs a bit more to do so.

One of my problems is that a lot of the literature on Gel/AGM batteries is about their use in 'float' (standby power) environments, not deep cycle marine environments. Some of the best articles are on manufacturers' sites, but they are written to promote a product line.

I'd appreciate input about people's own knowledge and experience, and links to authoritative articles on the Web.

[Fanie]

The rule with batteries in any kind of waters is simple. Keep them dry and the terminals out of the water. As far as I know you get spillproof battery boxes where you can ride the battries in.

Before fancy welders like we have today they used batteries to weld with. One must never underestimate to power of these every day used luxuries, even the small ones can be deadly when they explode.

There was a time one had to hand crank an engine to get it started. Can you imagine the Yamaha with a crank kandle ;)

Matt - Since the AWB used chlorine and brake fluid to make bombs with, it became news so everyone here now knows how to do it cheaply :D They did warn housewives who buys groceries not to put the chlorine granuals in a bag with daddy's brake fluid, in the case of a leak it could be fun.

He he... makes you look different at the female in the car next to you. Cant wait for the trafic light to change eh :D

[CDK]

You may remember from the chemistry lessons that Cl, Br, J and F are the halogens, something very similar to hooligans. An aggressive bunch that reacts with almost anything and therefore are almost never found as elements.
So the tale of Cl2 escaping is probably not true.

Many years ago I got a telephone call from the marina that my boat was unusually deep in the water. When I arrived I found the engine bay flooded, cause by a small tear in a Mercruiser bellows, cut by an oyster shell quite near the surface. In a few weeks time the engine bay was filled until the valve covers of the engines.
There were two fully charges batteries powering the electrolysis and total destruction of two hydraulic pumps, starters, alternators, ignition units and the complete wiring harness of two engines. Where the battery poles were, a crater had formed, so there was free interaction between seawater and battery acid, what were once heavy cables now were only empty hoses.
Yet there wasn't even the faintest smell of chlorine...

[chabrenas]

Thanks, CDK. Just the kind of tale I'm looking for. Anyone else got a story to tell? Or a chemistry lesson?

PS Sorry about the boat... Hope the insurance paid up.

[CDK]

They did!
In fact they paid for original Merc spare parts, like $890 for an alternator. I found refurbished parts for less than 1/3 and when the job was done, I invested their bonus in an Apelco LCD radar.
And the best automatic bilge pump I could find....

[chabrenas]

Howzit, Fanie. I'd forgotten about the AWB bomb-making technique, although I was back & forth through Mafikeng at the time.

Biggest engine I've ever hand cranked was a 2 cylinder Volvo diesel in an S&S 34. Decompression cams on, wind up slowly, then flip the cam levers....But since you only need to do that when you're in the thick of it all and find the starter button doesn't work, you've only got one chance.

[Fanie]

You were through Mafi-where ? :D

I'm always scared that if you try and pull start one of these big outboard engines it may backfire and actually wind you the wrong way round, which would leave you with extremely long thin arms.

We had a lister water pump on the farm when I was a kid. That was a real kicker.

As for chemistry, I find that, and stuff like medical stuff very interesting, but to remember those terms... I guess I have a poor memory, is why there's guys like you all, and Google for if one really needs the specifics.

[chabrenas]

Mafi-where
Mafeking/Mafikeng, Bhophutatswana. On my way from Gaborone to Vaalie-land and the Cape. Where are you? KZN?

[robherc]

Hmm, being that I'm one of the rare people who've had a bit of experience with pure Cl2 gas (from compressed cylinders, in Iraq, don't ask), I can tell you that before the chlorine does major damage to your lungs, you'll be screaming in pain! The stuff smells stronger than anything you'd stay near, and burns like fire once it gets in your nose. And I found (through involuntary exposure) that it actually takes quite a lot of it, or a lot of time exposed to it, to do any major damage to you (or at least to me). So I would count chlorine as dangerous the same as I count fire as dangerous...not like chloramine gas, which is something that's actually scary.

To sum all that jibberish up: Even if it DOES release significant amounts of Cl2 gas, nobody's likely to be injured by it unless they're incapacitated, inebriated, or incredibly stupid. Otherwise, you'll get outta the engine room & run the vents if it smells like chlorine so badly that you can't stand it, and it's making your nose, eyes, throat, and ches tburn.


chabrenas, I hope that helps for your blogs ;)

[chabrenas]

Thanks, robherc. I've seen and smelled chlorine gas (thick enough to be visibly green) in school chemistry labs, and in extracurricular chemistry at home. It is reckoned to be lethal over a period of several minutes at a concentration of 400 parts per million (versus carbon monoxide 1000ppm, phosgene 50ppm and arsine 10ppm. However, as you point out, the tiniest whiff of it has you choking and running for the exit.

I have now found a couple of articles saying that two poisonous gases are sometimes evolved from battery charging (in a normal environment, not with added salt water) - arsine (according to the list above, the most toxic of poison gases) and 'stabine'.

Arsine is arsenic trihydride, and can be odourless at its lethal concentration, but I have not been able to find out what stabine is, in spite of searching a couple of general and chemical dictionaries online. Can anyone here tell me? Presumably another hydride of an impurity or additive found in lead-acid batteries.

[chabrenas]

OK. Found it by inspired guess, knowing that antimony is used to stiffen some lead plates. It's STIBINE, not stabine, and it is antimony trihydride. It's about as toxic as arsine, but it smells like H2S (rotten eggs) so probably easier to notice. I've also worked out where the arsine comes from - impure zinc contains arsenic, and some plates and connectors contain zinc.

Batteries are nasty things, methinks. Pity we tend to keep them low down because they're heavy.

[mydauphin]

I think the goal for a boat builder professional or amateur besides all the functions and form , is safety. Simply put a boat has to be design to take being flipped over and it should return back straight. Batteries, fuel tanks, water tanks, heater, stoves, microwaves, generators and even your personal stuff should be firmly attached. That said propane, gasoline, solvents, acids should not be in the compartment with the people. or bilge. Improper ventilation, spark or accident can be a disaster in the making.

[chabrenas]

mydauphin: I agree strongly. Now would followers of this thread like to tell me what percentage of boats, that are used in conditions where even something as trivial as a sudden squall is likely, actually do have safe battery installations?

[Fanie]

I think many boats actually have safe battery installations. The use of sealed batteries enhance safety some. Again, I presonally think the battery acid itself has a far greater risk if it can leak out and mix with water in a hull. It can even cause blindness and severe skin burn, but will depend on how much water it mixes with and the circumstances.

I'm not from KZN. Do I look like a Zulu to you ? Butch is from KZN but it's not his fault :D

I'm from Gauteng-eleng-eleng, the crime capital of SA, Africa and the world.
The area we live in (Centurion) has THE highest crime rates because the ANC put up 5 squatter camps around us to vote us out here, regardless of the consequences.

[chabrenas]

Gauteng car plates - GP - stand for Gangsters' Paradise, I believe... You're a long way from your fishing grounds, aren't you, Fanie? I believe there may be some little ones in Centurion Lake, but...

They built a township on the edge of Franschhoek to try to rig the votes, too - and lots of other places.

I've just looked at ISO10133, which says batteries should not spill at 30° heel, and box should contain spill at 45°. Sounds OK for normal sailing conditions, but not for what I've heard folks arriving in Richards Bay from Madagascar describe...

Although they're still not in common, use, I reckon AGM batteries must be worth the money if you're doing serious ocean sailing. Even for the ordinary sailing boat, it would be nice to have the battery box in a cockpit locker rather than in the cabin, but I've never seen that done - but I'm out of touch with today's practices.

[Fanie]

Actually GP stands for 'groot poepol', and don't start with me being far from the coast. I know even 'groter poepolle' who lives right there at the waterfront and don't put foot on it. Can you believe that :(

I'm almost sure I've seen some boxes that is formed so that even if the battery rolls over the acid doesn't spill out. I use sealed batteries, so I have little concern with that. May be the way to go.

These sealed batteries, if not abused (high charge and discharge currents) makes very little gas. I cannot say that I ever smelled or seen gassing since I started using these. The old LA batteries boiled and was smelly, and they don't last too well with the hammering we put them through for trolling motors, lights and the likes.

I used to replace the trolling motor LA batteries every 6 months. I'm in the fourth year with these SLA's, and they just go.

Probably the biggest concern with batteries is not to install them in a fuel tank hatch. I've seen it done.

[pkoken]

We run 100% AGM batteries. The only time you are going to get outgassing is if you are in the process of destroying them :)

The valves are designed to remain closed in all "normal" conditions. The valves open in the battery case pressure is too high. Once you vent gas & electrolyte in an AGM battery it is GONE forever. You need precise charging an voltage regulation to prevent battery destruction.

Our AGMs are by Lifeline and they are going on 5 years old....

[Fanie]

Awww... that's nothing, weee had a battery... :D

Batteries are too heavy. holds too little energy and has too short a lifespan.

Can't we vote for the mini nuclear generator, half life 32 years, hot water on demand, full power 24/7, maintenance free, size and weight of one big battery. After 32 years you just add the second source and you have full power for the next 32 years and so on. Here is a power source your children can inherrit, and their children...

[chabrenas]

pkoken: Dead right. Anyway, they reckon most ordinary wet batteries die from poorly-controlled charging, so I guess the first thing is to install a properly-controlled battery charging system (now that the old ferro-resonant chargers are dead & buried and we can do proper 3-stage charging even with things you pick up in Wal-Mart or a car acessories chain).

Fanie: Yeah. And the more expensive the boat, the more likely it will sit unused on an expensive marina berth all year. Should we feel sorry for the owners, or just sigh at their inability to get their priorities right? So where do you go to fish?

[chabrenas]

size and weight of one big battery
Where can I buy one? Street market near Pelindaba?

[marshmat]

Probably the biggest concern with batteries is not to install them in a fuel tank hatch. I've seen it done. Or under a fibreglass lid in the swim platform... saw that at a boat show once, decent looking boat but that battery setup was really sketchy.
Our AGMs are by Lifeline and they are going on 5 years old.... I've been hearing a few good things about Lifeline AGMs. How deep do you draw yours down, Phil, before recharging?
Can't we vote for the mini nuclear generator, half life 32 years, hot water on demand, full power 24/7, maintenance free, size and weight of one big battery. After 32 years you just add the second source and you have full power for the next 32 years and so on. Here is a power source your children can inherrit, and their children...
Where can I buy one?
Hyperion is working on getting one of these into production, see http://www.hyperionpowergeneration.com/ The lump of fuel is the size of a softball and, according to the folks at Los Alamos, can't be reprocessed into a weapon. At 25 MWe when running a steam turbine, it would be roughly equivalent to a 33,500 hp diesel. The effective life is only 5 years though. Cost: about $25M.

[robherc]

Hyperion is working on getting one of these into production, see http://www.hyperionpowergeneration.com/ The lump of fuel is the size of a softball and, according to the folks at Los Alamos, can't be reprocessed into a weapon. At 25 MWe when running a steam turbine, it would be roughly equivalent to a 33,500 hp diesel. The effective life is only 5 years though. Cost: about $25M.

Hmmm, so can I get one with a lump of fuel roughly the size of a .25cal (6.3mm) BB, and run it at about 5KW for 15 years? ... I'm sure I could come up with about $15,000 for it...rofl!


(if you want to hear something truly spookey, I just picked numbers out of the air there; then when I checked the Wattage X Years of the two, the ratio was 5000/3....when I checked the prices, the ratio was EXACTLY 5000/3! Wish I could guess things that well when it actually mattered!!! rofl :eek: )

[robherc]

oops, 0.21cal fuel lump ;) (just checked the volumes)

[chabrenas]

Wish I could guess things that well when it actually mattered!!!
Maybe you will from now on. All that training has finally paid off...

[chabrenas]

O.25cal vs 0.21cal? Close enough for government work...

Wonder if this is going to up the budget for competitors in the next Vendée Globe?

[MattZ]

You may get some hydrogen chloride (HCl) gas, but very little since this gas is highly soluble in water.

If the sea water gets into the battery you have a different problem that could produce chlorine, and possibly increase the hydrogen output because any sodium metal produced by electrolysis will immediately react with water to produce hydrogen gas.

[chabrenas]

Thanks, MattZ. Can anyone post the equations for the reactions that take place?

[MattZ]

H+ + Cl- <----> HCl(aq)

Note the double ended arrow, this is a chemical equilibrium. The HCl could then come out of solution. It is a very toxic gas, and on contact with water it will readily dissolve in water to make hydrochloric acid. Due to the high dissociativity of HCl, the yield of HCl should be very small.

Na+ + e- -----> Na
2 Na + 2H20 ------> H2 + 2 OH-

[Submarine Tom]

Post number 4 on this thread claims an incorrect average ocean salinity of 2 - 3 %.

The correct figure is 3.9% by weight.

Tom

[MattZ]

Post number 4 on this thread claims an incorrect average ocean salinity of 2 - 3 %.

The correct figure is 3.9% by weight.

Tom

3.1% - 3.8%

Varies based on temperature and location. (Typically higher at the equator and poles, lower at the mid latitudes.