Battery Gas Venting

[STATUE]

Previous boat had an AGM battery, but had a pipe from battery box (mid ships) fed right to the stern, when once was an ordinary battery, the type requiring topping up with distilled water.

My (new to me) yacht has an ordinary battery for domestic use but no evidence of any venting facility.

Should I bother installing one ?

 

[Stemar]

There's a theoretical risk of hydrogen gas being given off, but it's much lighter than air, and next to impossible to keep in a locker, so it disperses quickly. I wouldn't say it's impossible for it to go bang on a boat, but it would take some very special circumstances.

If it gives off Hydrogen Sulphide, that's toxic, but stinks, so you'll know before it does any real damage. It's also a sign of a serious problem with the battery so, personally, I'd like to know if it's being given off rather than have it venting outside.

 

[RichardS]

Previous boat had an AGM battery, but had a pipe from battery box (mid ships) fed right to the stern, when once was an ordinary battery, the type requiring topping up with distilled water.

My (new to me) yacht has an ordinary battery for domestic use but no evidence of any venting facility.

Should I bother installing one ?

If you mean that the battery itself is fully sealed and does not have any vents in the top plate then you will not be able to fit one.

Richard

 

[Mistroma]

I had a box with a vent pipe on my previous boat (Southerly). Jeanneau don't vent their boats, at least on any model I've seen. However, I did see dis-colouration on the underside of the lid after a couple of years.

I fitted a ventilation system because I changed to Trojan T-105s and was living on the boat for 7 months at a time. The T-105s get to 14.8V when charging and eq. charge is about 16V and fizzes like mad. I rarely do an eq. charge because the SG values are always very similar. It was easy enough to fit a variable speed forced air ventilation system when modifying the box to take the T105s.

I probably wouldn't have bothered for normal weekend sailing.

The batteries on my old Southerly actually had little traps on the side with tubes leading to a larger vent pipe. I don't think I've seen that on modern flooded batteries and they just allow the gas to escape through the top (even the "sealed" low maintenance type, as they aren't actually sealed).

 

[Graham376]

Our Trojans are under the aft cabin double berth and not vented anywhere except that locker.

 

[VicS]

Previous boat had an AGM battery, but had a pipe from battery box (mid ships) fed right to the stern, when once was an ordinary battery, the type requiring topping up with distilled water.

My (new to me) yacht has an ordinary battery for domestic use but no evidence of any venting facility.

Should I bother installing one ?

Id expect your battery either has vented filler caps or is fitted with a common vent at one end or in one corner which may have a fitting to which a small vent pipe can be attached. The hole ( or holes) may be plugged for delivery in which case it is important to remove the plug .

I agree with what Steve says about hydrogen dispersing quickly but its worth remembering that if a battery gasses it produces hydrogen and oxygen in exactly the right proportions for maximum effect if the mixture were to be ignited.

 

[STATUE]

Well, there we are, perhaps I should have stayed awake during science lessons !

Thank you everyone for such considered response.

 

[dankilb]

I'm building a new battery box to move our 4 110AH AGMs from the top of a cockpit locker (not a great place for the weight...) to under an aft cabin berth, on our Jen 42'. The box is replacing a water tank so I'm using the route for the old filler hose to vent to a breather 'manifold' we have fitted high on the aft quarter topsides.

Because it's under a berth and without any natural ventilation (I might fit a PC fan for cooling), I definitely think our box should be vented. Some of our crew vape (skipper included!) so the thought of anything like that setting off the gas in an enclosed cabin doesn't bear thinking about.

 

[Graham376]

Because it's under a berth and without any natural ventilation (I might fit a PC fan for cooling), I definitely think our box should be vented. Some of our crew vape (skipper included!) so the thought of anything like that setting off the gas in an enclosed cabin doesn't bear thinking about.

I think your thinking is way over the top. A battery may explode if filler caps are off and naked flame very close but the gas content in a cabin would be so tiny there's no chance of an explosion.

 

[PaulRainbow]

I'm building a new battery box to move our 4 110AH AGMs from the top of a cockpit locker (not a great place for the weight...) to under an aft cabin berth, on our Jen 42'. The box is replacing a water tank so I'm using the route for the old filler hose to vent to a breather 'manifold' we have fitted high on the aft quarter topsides.

Because it's under a berth and without any natural ventilation (I might fit a PC fan for cooling), I definitely think our box should be vented. Some of our crew vape (skipper included!) so the thought of anything like that setting off the gas in an enclosed cabin doesn't bear thinking about.

Absolutely no chance of that.

 

[footsoldier]

I'm very much in favour of venting battery boxes after two salutary experiences, both on delivery trips.

First wasn't too bad - running with engine on, myself and the other guy both started feeling nauseous after each trip below to the chart table. As soon as the chart table light was lit I could see a blue haze in the air. Further investigation showed the cranking battery, under the sole, had partially melted and fumes were jetting out of the resultant hole.

Second could have been serious. Again under motor, sharing an aft cabin, we came off watch exhausted and both immediately fell asleep. I was in one bunk, my mate was in a double which sat over the battery box, containing six large truck batteries. Six hours later, the indignant watch-keeper came below to ask if we were ever going to relieve him. He found the cabin full of acrid fumes - he managed to rouse me and I staggered out, but the other guy was semi-comatose and needed help. Fresh air soon revived me, although I had the mother of all headaches and a very sore throat - other guy was quite bad, couldn't speak because of his throat, lost all sense of balance, vomiting etc. Took him 24 hrs to more or less recover. Again, all six batteries had cooked off due to a faulty regulator.

Ever since I have been understandably wary of batteries and the location of battery boxes.

 

[PaulRainbow]

In normal use, gassing of most batteries will be about zero. Deep cycle, open cell, batteries will gas a little, but not enough to worry about, other than not having sparks and open flames in the battery box whilst they are on full charge. Add some extra caution of they are being equalised, just to be safe.

If a cell shorts you have a circa 10v battery, your charger will see that as a flat battery and try to charge it at something like 14.4v. This will boil the battery and result in a lot of gassing and hydrogen production. A spark or open flame anywhere near the battery is very likely to cause an explosion. If the batteries are beneath a berth or sofa, the chances of creating an explosion with a naked flame in saloon/cabin are about zero.

Whilst they do exist, it's a rare leisure boat that doesn't have its batteries somewhere in the accommodation.

It's also worth knowing that most Co alarms will be set off by excess hydrogen. We do all have Co alarms onboard, don't we ? Before someone says that they don't need a Co alarm, because they have nothing onboard that can create Co, think again. You can get enough Co in your boat from someone elses engine or genny. I have been onboard a boat when the Co alarms went off as the result of a genny on the deck of an adjacent boat. There was also a couple that almost died on the broads a couple of years ago as the result of Co emissions from another boats petrol engines, they didn't have a Co alarm.

A few years ago i had two leisure batteries fail at the same time, both with shorted cells. Perhaps one failed and charger finished the other one off, who knows. The result was, the charger stayed at 14.4v and boiled both batteries, badly. The first i knew was when the Co alarm went off. Nothing had been on to create Co, after a check outside to make sure no-one was running an engine, i looked under the saloon sofa and saw the boiling batteries (open wet cell). I closed the sofa base and turned the charger off. Left for a while o let the hydrogen disperse and some new batteries.

 

[dankilb]

I think your thinking is way over the top.

Absolutely no chance of that.

Good to know... I was only being semi-serious regarding the risk of a spark. More as per @footsoldier’s experience - knowing this cabin/berth is most likely to be used by guests/crew/kids etc., I want the mutual reassurance of the batteries venting to atmosphere.

I note that on most modern production boats - based on YT videos etc. - batteries don’t seem to be vented where they’re factory installed under settees or floors. Presume that reflects the low risk with AGMs? But for our installation, seeing as suitable plumbing is already there, there’s no reason not to vent the box.

 

[PaulRainbow]

Good to know... I was only being semi-serious regarding the risk of a spark. More as per @footsoldier’s experience - knowing this cabin/berth is most likely to be used by guests/crew/kids etc., I want the mutual reassurance of the batteries venting to atmosphere.

I note that on most modern production boats - based on YT videos etc. - batteries don’t seem to be vented where they’re factory installed under settees or floors. Presume that reflects the low risk with AGMs? But for our installation, seeing as suitable plumbing is already there, there’s no reason not to vent the box.

Lots of production boats with batteries under berths and sofas Dan, no venting in most cases. If you want to vent the box, Hydrogen is lighter than air, so as long as the vent pipe has a rise you won't need a fan. If you go this route, the battery box would need to be sealed for it to make any sense.

Don't forget the Co alarm in the cabin

 

[reeac]

My much- loved Jag. XJ8 had its battery very well hidden away in its own compartment in the boot with no ventilation. It was 15 years old when I sold the car and still as good as new. Admittedly the useage in a car is less demanding than as a house battery on a boat as it probably never saw any big charging currents.

 

[geem]

I'm very much in favour of venting battery boxes after two salutary experiences, both on delivery trips.

First wasn't too bad - running with engine on, myself and the other guy both started feeling nauseous after each trip below to the chart table. As soon as the chart table light was lit I could see a blue haze in the air. Further investigation showed the cranking battery, under the sole, had partially melted and fumes were jetting out of the resultant hole.

Second could have been serious. Again under motor, sharing an aft cabin, we came off watch exhausted and both immediately fell asleep. I was in one bunk, my mate was in a double which sat over the battery box, containing six large truck batteries. Six hours later, the indignant watch-keeper came below to ask if we were ever going to relieve him. He found the cabin full of acrid fumes - he managed to rouse me and I staggered out, but the other guy was semi-comatose and needed help. Fresh air soon revived me, although I had the mother of all headaches and a very sore throat - other guy was quite bad, couldn't speak because of his throat, lost all sense of balance, vomiting etc. Took him 24 hrs to more or less recover. Again, all six batteries had cooked off due to a faulty regulator.

Ever since I have been understandably wary of batteries and the location of battery boxes.

We have large back lit LED battery voltmeters in the saloon. You cant miss them. If there was a battery voltage problem it is immediately evident. Its a simple system but very useful. Knowing battery voltage is very important

 

[dankilb]

Lots of production boats with batteries under berths and sofas Dan, no venting in most cases. If you want to vent the box, Hydrogen is lighter than air, so as long as the vent pipe has a rise you won't need a fan. If you go this route, the battery box would need to be sealed for it to make any sense.

Don't forget the Co alarm in the cabin

Yup that’s the plan. The lid of the box I’m building fits into a recess - just for clearance, but which will also make sealing it relatively easy.

All this means that venting it is one of those ‘just because we can’ things! But I totally appreciate that it isn’t strictly necessary and wouldn’t warrant major mods to the design/installation.

Cheers for everyone’s input. Every day’s a school day!

 

[penberth3]

.......Before someone says that they don't need a Co alarm, because they have nothing onboard that can create Co, think again. You can get enough Co in your boat from someone elses engine or genny. I have been onboard a boat when the Co alarms went off as the result of a genny on the deck of an adjacent boat. There was also a couple that almost died on the broads a couple of years ago as the result of Co emissions from another boats petrol engines, they didn't have a Co alarm.......

A near miss, but there's been at least one recent fatality because of this.