Haven't-a-Clue
Well-Known Member
What an amazing site! I can't imagine not being able to find just about anything there. Thanks.
Another battery question - deeply sorry.
- Thread starter mick
- Start date
boatmike
Well-Known Member
Mick, I was the one who started your paranoia probably on a previous thread.
Let me see if I can put this in perspective.
Firstly don't listen to people who say Naa... can't happen. There is one guy on this thread who has had it happen. But lets put it in perspective. It's a rare occurrence but very simple to take steps against.
Lets just recap that batteries can explode due to an internal short or by causing a build up of hydrogen external to the battery.
To insure yourself against both
1. Always check and replenish electrolyte levels regularly. Dry batteries are dangerous.
2. Don't put them somewhere where if it does happen it will cause injury.
3. Don't let them overheat.
4. vent the compartment they are in at the top.
The fan idea is excellent but do ensure it's a brushless or fire-safe motor fan so does not cause sparks. /forums/images/graemlins/blush.gif
The other thing I would say is ensure the air has somewhere to go. If it vents the air into the engine compartment ensure there is a vent at the top of that compartment. (There usually is)
As you intimate, the risk of having a problem from external hydrogen if the engine is running and charging the batteries is low, especially if they are vented into the engine compartment as there is a constant air change in that case. They can still blow due to an internal short though if they run out of water so check regularly especially if you have a smart charger.
The risk is at its highest when charging by other means (shore supply, generator, windy blow gennys or even solar panels) as there is no forced air supply then and if the batteries are in an unvented closed compartment it could be a danger.
You can offset this risk by a vertical vent to the compartment or just leaving the top off when charging as someone sensibly said. A small plastic tube out of the top would be good too if you can arrange it even if it vents into the cabin. As again someone already said hydrogen is light and will seek an exit through hatches etc. The relative volumes of an average cabin to the amount of hydrogen you are going to produce with little batteries means so long as its not in a small enclosed box you shouldn't have a problem anyway. Vent to outside preferably but to the cabin if that's not easy to achieve.
If you do these things you will not become a statistic. The guys that do are the ones that say Naa! can't happen!
Enjoy your sailing!
Let me see if I can put this in perspective.
Firstly don't listen to people who say Naa... can't happen. There is one guy on this thread who has had it happen. But lets put it in perspective. It's a rare occurrence but very simple to take steps against.
Lets just recap that batteries can explode due to an internal short or by causing a build up of hydrogen external to the battery.
To insure yourself against both
1. Always check and replenish electrolyte levels regularly. Dry batteries are dangerous.
2. Don't put them somewhere where if it does happen it will cause injury.
3. Don't let them overheat.
4. vent the compartment they are in at the top.
The fan idea is excellent but do ensure it's a brushless or fire-safe motor fan so does not cause sparks. /forums/images/graemlins/blush.gif
The other thing I would say is ensure the air has somewhere to go. If it vents the air into the engine compartment ensure there is a vent at the top of that compartment. (There usually is)
As you intimate, the risk of having a problem from external hydrogen if the engine is running and charging the batteries is low, especially if they are vented into the engine compartment as there is a constant air change in that case. They can still blow due to an internal short though if they run out of water so check regularly especially if you have a smart charger.
The risk is at its highest when charging by other means (shore supply, generator, windy blow gennys or even solar panels) as there is no forced air supply then and if the batteries are in an unvented closed compartment it could be a danger.
You can offset this risk by a vertical vent to the compartment or just leaving the top off when charging as someone sensibly said. A small plastic tube out of the top would be good too if you can arrange it even if it vents into the cabin. As again someone already said hydrogen is light and will seek an exit through hatches etc. The relative volumes of an average cabin to the amount of hydrogen you are going to produce with little batteries means so long as its not in a small enclosed box you shouldn't have a problem anyway. Vent to outside preferably but to the cabin if that's not easy to achieve.
If you do these things you will not become a statistic. The guys that do are the ones that say Naa! can't happen!
Enjoy your sailing!
VicS
Well-Known Member
The solution as far as safely venting batteries is concerned is to buy batteries that have a vent connection and to connect these up to lead any gases away and safely discharge them.
All my batteries (boat and cars )have vent connections on them so I assume it is now standard practice. I have to admit though that the only one actually connected to anything is the one in swmbo's car.
All my batteries (boat and cars )have vent connections on them so I assume it is now standard practice. I have to admit though that the only one actually connected to anything is the one in swmbo's car.
chriscallender
Well-Known Member
Well, I'd assume the risks are pretty small, mainly because I've got the same arrangement and its never come up as an issue on any survey - and I know the surveryor has been pretty thorough everywhere else.
On anecdotal evidence, I've twice experienced major overcharging and gassing of batteries on cars due to alternator regulators packing in and I have a feeling the stench will alert you pretty quickly that something is wrong, hydrogen isn't the only nasty you will be experiencing if the charging goes wrong. No need for a battery warning light for overvoltage....although one of the cars had one.
I can also tell one battery explosion story, but in that case it blew instantly from a dead external short circuit that no amount of venting would help with so irrelevant here. Hint: Not good for your short term health to connect both jump leads to a truck battery when the other ends are touching against each other - and no it wasn't me! As I said, totally irrelevant to this discussion
But why waste the opportunity of telling a scary story?
On anecdotal evidence, I've twice experienced major overcharging and gassing of batteries on cars due to alternator regulators packing in and I have a feeling the stench will alert you pretty quickly that something is wrong, hydrogen isn't the only nasty you will be experiencing if the charging goes wrong. No need for a battery warning light for overvoltage....although one of the cars had one.
I can also tell one battery explosion story, but in that case it blew instantly from a dead external short circuit that no amount of venting would help with so irrelevant here. Hint: Not good for your short term health to connect both jump leads to a truck battery when the other ends are touching against each other - and no it wasn't me! As I said, totally irrelevant to this discussion
But why waste the opportunity of telling a scary story?
boatmike
Well-Known Member
Well that's one solution Vic but firstly not all batteries have them, and secondly it won't stop a neglected battery exploding internally. All this started with me saying it was a bad (frankly awful) idea puting batteries in unvented boxes. It still is.
VicS
Well-Known Member
[ QUOTE ]
won't stop a neglected battery exploding ............. it was a bad (frankly awful) idea putting batteries in unvented boxes
[/ QUOTE ] So what is needed is a box strong enough to contain an explosion, vented to prevent the build up of hydrogen, and with cooling to prevent the batteries overheating.
<span style="color:white"> ....................................... </span> Better get the designers hat on!
won't stop a neglected battery exploding ............. it was a bad (frankly awful) idea putting batteries in unvented boxes
[/ QUOTE ] So what is needed is a box strong enough to contain an explosion, vented to prevent the build up of hydrogen, and with cooling to prevent the batteries overheating.
<span style="color:white"> ....................................... </span> Better get the designers hat on!
William_H
Well-Known Member
Light aircraft are required by design standards to have ventilation in the battery compartment. The compartment is usually sealed Al box.
The simple venting is a tube about 10mm diameter going to outside air with an angle cut so an open end faces the slipstream. Similarly another tube has a cut facing aft to suck the air out.
For a boat you might want larger tubing as the aircraft has a healthy sliptream to force ventilation.
However considering that the average light aircraft has a smaller battery than your car but with very similar charging arrangements then a boats ventilation requirements might be a lot greater than an aircraft's.
The white powder referred to earlier is obviously baking soda or similar to neutralise any acidity in the fumes. This to minimise corrosion of metal structure near the vent. However these bottles are not used on aircraft. I guess for weight considerations and because it is all inspected often.
If you use a shore charger of high current or a smart charger then ventilation should be considered. olewill
The simple venting is a tube about 10mm diameter going to outside air with an angle cut so an open end faces the slipstream. Similarly another tube has a cut facing aft to suck the air out.
For a boat you might want larger tubing as the aircraft has a healthy sliptream to force ventilation.
However considering that the average light aircraft has a smaller battery than your car but with very similar charging arrangements then a boats ventilation requirements might be a lot greater than an aircraft's.
The white powder referred to earlier is obviously baking soda or similar to neutralise any acidity in the fumes. This to minimise corrosion of metal structure near the vent. However these bottles are not used on aircraft. I guess for weight considerations and because it is all inspected often.
If you use a shore charger of high current or a smart charger then ventilation should be considered. olewill
boatmike
Well-Known Member
Hi Olewill! Yes I actually started my working life in the Aircraft Industry. Did an apprenticeship with CAV/Rotax actually (now Lucas Aerospace) The Rotax side did Aircraft electrical systems and actuators and CAV are fuel system related of course. Then I moved to ship and boat design and build. That's the perspective I speak from so I know the setup on light aircraft and you are spot on. To answer your's and Vics points, any explosion, especially one that could nuke your electrical system on a plane is even more serious than on a boat. Luckily on a boat the weight restrictions are far less. Having built three fast ferries just before I retired, with DNV and MCA rules to satisfy, both the cranking and service batteries were in a seperate compartment adjacent to the engine room with steel bulkheads and a vent above to a dorade on the aft deck and a fully latched door. Other arrangements I have seen put the batteries in the engine room itself but these engine rooms have honking great big air circulation fans and exhaust to deck level. Even then MCA like to see them near the air exit point and as far away from engines etc as possible and away from escape hatches and walkways to minimise the H&S risks.
My real pet hate are the plastic lightweight unvented boxes sold in chandlers to put batteries in. They achieve sod all that you can't achieve with restraining straps and hold down blocks and introduce an entirely unnecessary risk of Hydrogen build up. I owned a boat once with one of these monsters on and punched a hole in the top to vent it. Builders of small yachts sometimes design the most horrific things into them that no class society would allow as illustrated with pictures here. The owners, understandably perhaps often say " Well it was designed that way so it must be OK" Wrong! It.s easy and inexpensive to get it right and that's why I persist with posts like this.
My real pet hate are the plastic lightweight unvented boxes sold in chandlers to put batteries in. They achieve sod all that you can't achieve with restraining straps and hold down blocks and introduce an entirely unnecessary risk of Hydrogen build up. I owned a boat once with one of these monsters on and punched a hole in the top to vent it. Builders of small yachts sometimes design the most horrific things into them that no class society would allow as illustrated with pictures here. The owners, understandably perhaps often say " Well it was designed that way so it must be OK" Wrong! It.s easy and inexpensive to get it right and that's why I persist with posts like this.
whipper_snapper
Well-Known Member
I always thought that venting into the engine room was perfectly safe, becuase the engine itself is a blooming great exhaust fan. It pulls in and burns any hydrogen floating around. If the arrangement is such that you cannot charge the battery without the engine running, then it should be perfectly OK and hydrogen build-up should be impossible, Provided
1, the engine air is not ducted directly into the engine's air intake (on most systems I have seen there is a big engine air inlet but it opens into the engine room)
2. The batteries cannot be charged by a remote genny or a shore power supply. If they are, you need to do something special when that is happening.
I remember discussing this with a surveyor who was coding a big boat and he was very happy with this philosophy.
1, the engine air is not ducted directly into the engine's air intake (on most systems I have seen there is a big engine air inlet but it opens into the engine room)
2. The batteries cannot be charged by a remote genny or a shore power supply. If they are, you need to do something special when that is happening.
I remember discussing this with a surveyor who was coding a big boat and he was very happy with this philosophy.
maxi77
Well-Known Member
Certainly the old Diesel electric submarines disposed of vented hydrogen when snorting through the engines, the battery compartment vents exhausted direct into the engine air intakes, but as I said before they were big high voltage batteries so lots of hydrogen. Also remeber a charging battery only gives off hydrogen above a certain voltage, 13.8 I think but the memory id dim. and only gives off a lot of hydrogen when equalising, something rarely done on boat batterires. This is in my opinion a 'dont be stupid' thing but equally a 'don't panic as well.
Now allowing batteries to short, either internally or externally, that is something to take every step to ensure doesn't happen. Shorted batteries make big bangs with lots of heat.
Now allowing batteries to short, either internally or externally, that is something to take every step to ensure doesn't happen. Shorted batteries make big bangs with lots of heat.
mick
Well-Known Member
My God, the things people know. I've found the whole thread v. interesting, so thanks to all. I'm going to run plastic piping from the vents, through the wooden lid, under the cushion and out into the quarter berth area - just in case.
charles_reed
Well-Known Member
Plastic battery boxes
Yes totally useless for batteries, but quite good for holding the kedge chain.
In reading this chain I've been impressed by the justifiable paranoia of some - surely those with a "smart" controller (TWC, Adverc, Stirling) are far more at risk - I've had a battery boil due to one faulty cell.
Once one has experienced that high-pitched sound of an hydrogen explosion (and lost eyebrows into the bargain) one won't want to repeat it.
Oh! no fancy facilities for my batteries the twin box of one is vented striaght into the engine compartment and the other is unboxed (but strapped down) in the large fore locker.
Yes totally useless for batteries, but quite good for holding the kedge chain.
In reading this chain I've been impressed by the justifiable paranoia of some - surely those with a "smart" controller (TWC, Adverc, Stirling) are far more at risk - I've had a battery boil due to one faulty cell.
Once one has experienced that high-pitched sound of an hydrogen explosion (and lost eyebrows into the bargain) one won't want to repeat it.
Oh! no fancy facilities for my batteries the twin box of one is vented striaght into the engine compartment and the other is unboxed (but strapped down) in the large fore locker.
boatmike
Well-Known Member
You are not wrong in the context of small yachts with vented engine rooms. In practice most are well vented anyway and usually the vents are in the top (If they were in the bottom they would let water in instead of air... Doh!)