Do I need a battery box ?

affinite

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I plan to fit 2 additional 110Ah batteries at easter but Im just wondering if they need to be in a plastic battery box. They will be sealed, maintenance free type so no chance of splilling acid ? They will be under a sturdy wooden seat with good restraints to stop them moving, so physically secure, and Ill put appropriate electrical insulation around to prevent shorting the terminals.
So - do I really need a plastic battery box ?
What does the panel think - false economy? - If so why ?
Thanks
Steve
 

Cloven

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Re: Do I need a bettery box ?

Steve - I'm about to do exactly the same and do not plan to use battery boxes - however I'll be intersted in other replies.
 

jerryat

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Re: Do I need a bettery box ?

Well I have a five battery set-up (four service - one engine start) and none of them are in battery boxes, so I definitely wouldn't bother if I were you.

As with yours, mine are strapped down tight and cannot move, and are maintenance-free. I think the battery box idea came from the days of pre-M-F batteries when it was desirable to keep any spilled acid within safe bounds. Whilst M-F batteries aren't perfect, they're a lot better is this respect.

Save your money. /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif
 

simonfraser

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Re: Do I need a bettery box ?

if it's sealed i'd think not. protect the terminals, of course !
and without a box it's easier to see the magic eye indicator.
 

boatmike

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The objective of battery boxes is not primarily to restrain spilt acid although that's good to do. It is to contain hydrogen that the batteries give off. Deep cycle batteries and batteries on high charge give off gas. MCA rules for commercial vessels (not applicable to small yachts) require batteries to be in a sealed compartment or container with a vent to outside atmosphere above (hydrogen being lighter than air). I have seen batteries mounted in containers with no vent at all, which just causes gas build up inside which is dangerous, vented downwards which is what you should do for gas bottles because that's heavier than air, and batteries mounted with no box at all. The latter is fine, but not in a closed compartment where gas can build up such as a cabin. Its also arguable that its OK in an engine compartment but only if it is very well ventilated. Not a good idea otherwise because when starting a diesel after batteries have been charged it could ingest hydrogen (bang!) If the battery can gas safely to open atmosphere the relatively small amount of gas a battery of the size you are using gives off is not a risk, but don't let it gas anywhere near electrical equipment where a spark could ignite the gas either and this could well mean not in the engine compartment too. In practice use your judgement. I would say if the seat you are talking about is in the cockpit it's fine. In the cabin it's not.
 

affinite

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Thx Mike
The seat Im talking about IS in the cabin so your point re gas does make me a little concerned. Also - like a lot of boats my other 3 batteries are mounted under the bunks in the aft cabin and open to the engine compartment. (I suspect that this is the original builders choice of location ??)
Sounds like a good job I dont smoke in bed (actually, it sounds like a good job I dont smoke at all)
 

PetiteFleur

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My batteries, two 110ah low maintenance leisure type are in a wooden box beneath the companionway steps, with a clipped down lid. Additionally I've fitted wooden strips around the base and a strap to prevent them moving around. The battery position is as built in '79. It would be very difficult to vent the compartment as it's below the waterline. Never had any problem and was passed by two surveyors on purchase(apart from strapping the batteries down).
 

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I am trying to understand this in the context of a small craft.

As hydrogen is lighter than air then a 'box' is presumably not very useful - it is the cover part that would control any gas build up.

But then again, I would have thought that you don't want to allow a concentration of hrdrogen to develop, so an open 'box' and area may be more useful.

/forums/images/graemlins/confused.gif
 

boatmike

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The point I am making is that a completely closed box does nothing useful if the batteries are mounted securely otherwise and could in fact be a danger as Hydrogen can build up in the box rather than venting naturally. If you want to do a really professional job the box should have a top vent which is lead away to the outside through a pipe. Many yachts are built with batteries in the engine compartment and elsewhere for cheapness and convenience though. Neither Lloyds or MCA would give a class or safety certificate for such an installation but as small yachts don't need either builders do the cheap and easy thing. Its OK if the cautions I mentioned are taken into account. An installation that puts them under an external vent so that hydrogen escapes upwards and does not build up in the compartment is a good compromise. Likewise its not ideal to place them next to a starter motor with sparky brushgear or right under the engine intake.
 

Pye_End

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Understood.

Since I had assumed that they were for acid containment I will look at one of my boxes in a new light. It may gain a couple of extra holes in the lid!
 

boatmike

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It would be very difficult to vent the compartment as it's below the waterline. Never had any problem and was passed by two surveyors on purchase(apart from strapping the batteries down).
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Firstly, Hydrogen RISES so its easy to vent the box with a pipe going up to a convenient place above even if they are in the bilge. No point unless the box lid is gas tight though. Secondly it's not necessarily dangerous if they are sited reasonably well. The main thing to remember is to keep them in a position where hydrogen CAN rise and escape and won't build up over time.
 

boatmike

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Is the compartment where you want the new battery entirely closed? If it is can you simply drill a hole in the top somewhere, fit a plastic skin fitting, and lead the pipe somewhere useful like the chain locker? A grill at the bottom then and you would pass an MCA safety check! (Not that you need to of course)
If the others are in a compartment that is vented to the engine room AT THE TOP of the compartment they are in it's probably OK. Engine rooms have to be vented to allow air in to the engine. These vents are usually at the top somewhere so while not ideal would probably ensure no Hydrogen build up.
Don't become paranoid! Just think.... Over time, especially if I leave the boat on shore supply to charge up deeply discharged batteries, these little boogers will give off hydrogen. Not a lot, but can it build up? If so think it wants to go up. This is great! Its not like butane that sinks to the bilges, just make sure it can get out. Common sense can prevail! I once did see a boat where the bloke had stuffed a battery right under his cooker though..... not good!
 

sarabande

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Ummm ! I wonder about the point made of putting a battery into a box ' to contain the hydrogen'.

Unless the box is hermetically sealed, hydrogen (if any is produced at all) will float UPWARDS into the cabin space and then disperse.

You will need to have a real problem with the battery malfunctioning to produce enough hydrogen to have an explosion onboard.

If an engine ingests hydrogen, it will need to be (a) a petrol one
(b) have the gas in a reasonable stochiometric ratio (hydrogen:eek:xygen basically) for the gas to burn. The amount of hydrogen gas in a compressed engine cylinder is not likely to be enough to blow up an engine.

The point is, however, well made that ventilation is the key to battery boxes and spaces.
 

affinite

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Wow I didn't expect "stochiometric ratios" to be part of my problem !! /forums/images/graemlins/wink.gif
The compartment I have in mind for the new batteries is simply under a bench seat in the cabin. It does have a vent because the battery charger is also in that compartment and the bench is directly under the main salon hatch - which is always open when moored or at anchor (Greece) so sounds like I might have the ventillation suggested by Mike. The existing batteries under the bed might need a little help though. I was thinking of putting a high level vent in the engine compartment anyway to get rid of excess heat after motoring so I think a cunning plan is developing ...
 

Stemar

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As others have said, the hydrogen will escape upwards into the cabin. which is, presumably reasonably well ventilated. It will then escape to the atmosphere long before you'll get anywhere near a dangerous concentration, even in a gross overcharging situation. There are circumstances when a battery can give off H2S, which is toxic, but stinks (rotten eggs) so bad you wouldn't be able to stay anywhere there's enough to do you any harm.

My domestic battery is in a locker in the cabin and a Starlight 25 I sail on has a bank of batteries under a settee with no problems. Put your batteries where you like, just make sure they won't escape if you get knocked down.
 

DaveS

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I think I've seen this (or similar) quoted before. I'm a bit mystified, however, since, as I understand it, a battery only gives off hydrogen when being charged vigorously. Why would there be hydrogen in the vicinity of a battery in a vehicle that's been sitting idle? The same argument applies to the jump charge issue (in the same reference): if the last connection is made to the dead battery it may well spark, but why should there be any hydrogen near the dead battery?
 

boatmike

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It's not the fact that it's "dead." Batteries are seldom dead and inert it's just deeply discharged and was probably dry.
All batteries give off hydrogen gas. The problem if you have one that needs jump starting or high charge is that you are passing a high current through it which can cause heat and distortion of plates. Battery sparks internally in this case and explodes. Thats one problem. More commonly what I was talking about before on boats was not putting the battery in an external enclosure that is not vented, like an unvented box. This causes a build up of hydrogen external to the battery that can cause an external explosion if there is a spark of any kind.
The biggest danger on boats is that we deeply discharge our batteries when sailing and with smart chargers etc. we pile the amps back in fast. This causes quite a considerable amount of hydrogen and oxygen to be given off (it's actually how the water level goes down so fast) and this must be vented. If it is, no problem, if its not, or the water is entirely converted to hydrogen and oxygen gas and "boils dry" you can have a dangerous situation. So don't just install them in a safe place. Inspect and maintain water levels often.
 
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