Ideas for ventilating battery compartment

[Paul L]

How 'bout using a hydrocap to avoid the gas issue?

[a64pilot]

Has anyone ever heard of a battery box explosion?
I've heard of frozen batteries exploding when you tried to jump start them on an automobile, but have never heard of any others?

Worry about the Propane, hydrogen I believe won't be an issue unless you seal the batteries in.

[masonc]

Originally Posted by kas_1611

And everything on your boat is EX or EEX rated? All those cable connections, electrical gizmos, switches etc?

I was working in our workshop last month in the middle of the day when the solar was charging the battery. Our power comes from 8 x Trojan IND9 batteries. While we were grinding some metal, we heard a loud pop. The hydrogen off the battery had exploded, ignited by the grinding sparks. As they are sitting in a corner with no enclosure, there was no damage, but if they had been enclosed, the enclosure would have been blown apart.
Best to be safe.

[Mycroft]

Yes, it's nice to get rid of the gases, but it's also good to ventilate for heat as well. Higher temps expand the fluid in the batteries and decrease their lifespan.

I've set up my engine ventilation to draw out hot air from the engine compartment to a stern funnel vent which brings cool air over the batteries and into the eng comp.

[Cheechako]

I've not worried too much about it in the past, but there is a potential for explosive gases in theory. A simple hose connected to the compartment and run up a few feet creates a chimney effect with no fan needed.
However, the majority of power boats out there has wet cell batteries in those plastic boxes they sell for that purpose. Those boxes are not designed to be air tight and aren't even remotely tight at all.
Also, engine rooms have fans for extraction.

[Bill Seal]

Interesting thought;
Computer fans are brushless, and thus can't produce sparks, while bilge blower fans have brushes.

[ZULU40]

hydrogen is not your main problem
salt water mixed with the electrolyte, perhaps from cracked cells, produces deadly chlorine gas
and if you were wondering, it isnt a passive way to die

[Dockhead]

Originally Posted by Bill Seal

Interesting thought;
Computer fans are brushless, and thus can't produce sparks, while bilge blower fans have brushes.

Good bilge blowers are ignition protected

[rwidman]

This all seems like a lot of fuss for something that shouldn't be a problem. The designers of the boat should have provided the necessary ventilation.

If it bothers you. it seems like simply using sealed batteries (AGM or Gel) would be far simpler than rigging up fans and ductwork.

[zboss]

Originally Posted by rwidman

This all seems like a lot of fuss for something that shouldn't be a problem. The designers of the boat should have provided the necessary ventilation.

If it bothers you. it seems like simply using sealed batteries (AGM or Gel) would be far simpler than rigging up fans and ductwork.

I agree... I'm not sure I have ever heard of a hydrogen explosion on a boat. More often its propane, which is probably multitudes more likely to explode on a boat. Even if one or two hydrogen accidents did happen over the last decade, this leads to the conclusion that the apparent risk is quite low.

I was thinking the same thing, that if you are that concerned then you should switch battery types.

[Snowpetrel]

Originally Posted by GILow

I dunno mate. I suppose that shed would fit on the foredeck but it is gonna play merry hell with our windward performance and I think it might foul the staysail.

Ha, I just like the video of the battery going "pop".. a pretty extreme example of what can go wrong.

I am not sure exactly where the likely danger lies with them, but I suspect its only when overcharging and near the vents in the top as the hydrogen and oxygen spew out.

I dont know if ventilation will help much in this case, isolation from sources of ignition is the best bet?

[GILow]

Isolation is all very well but I tend to take the pessimistic view that any accumulation will, sooner or later, cause problems. Dad blew a battery apart in the shed one afternoon by disconnecting the charge lead while the charger was running. We heard the bang from in the house. Blew the battery side clean off but he was mostly unscathed.

His hearing isn't too great these days.

Matt

[Snowpetrel]

^^ Interesting Matt, and ouch, I hope the acid wasnt to nasty for him. But thats an example of what I was refering to, the whole shed didn't blow, it was just the battery and the immediate area around it that exploded. Other batteries I have seen blow have also exploded the battery with minimal external damage except for the acid wash.

I guess I am speculating that it is the high concentration immediately venting from and inside the battery that is dangerous, and the gas quickly enough disperses to a non flammable concentration in most cases outside the battery with basic ventilation? At any rate I haven't heard of any big explosions on yachts due to hydrogen gas accumulating away from the battery, but on the ships we had a separate battery room with good ventilation. Maybe it is a risk, but my guy feeling is that the real risk is due to overcharging. Good ventilation will reduce the risk, but not eliminate it if the ignition source gets close enough to a vent?

What happens to sealed batterys if they are overcharged? As I understand it they still can vent and explode.

This is an interesting link, they talk of very small vent requirements?

http://caravanandmotorhomebooks.com/...tion-is-vital/

[TeddyDiver]

Reading How batteries can explode - and how to avoid it - Yachting Monthly
A few points. Inside a LA battery there's while charging explosive mixture of oxygen and hydrogen. In a sealed battery this mixture is present all times. Any over charging causes this mixture to vent outside the battery. If the PP (partial pressure) of hydrogen is over 0.01Bar the risk of explosion is imminent and will occur if there's any ignition source present.
Estimating the venting requirement allways consider the worst case scenario. Regulated charger controllers might malfunction sometime (IMO eventually they do) and one outcome might be full charging capacity into a allmost fully charged battery bank.

BR Teddy

[GILow]

Originally Posted by Snowpetrel

^^ Interesting Matt, and ouch, I hope the acid wasnt to nasty for him. But thats an example of what I was refering to, the whole shed didn't blow, it was just the battery and the immediate area around it that exploded. Other batteries I have seen blow have also exploded the battery with minimal external damage except for the acid wash.

True, I can't imagine blowing up the boat, but still, blowing up the battery bank while at sea could be a right PITA, not to mention a bit dangerous once nav lights are gone, auto pilot, radar etc.