Battery bank in aft cabin?

Tintin

Tintin

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I have a conundrum.

My boat, a Beneteau 325, currently has its house batteries under the boards in the aft cabin. Its a good location, on the cable run from engine to switch panel, main switches on bulkhead, and possibly room for a 3rd battery.

As i am currently doing an electrical refit i have looked at increasing battery capacity (kids, tv, fridge etc...) and while I could fit a 3rd 110ah battery in the current space under the aft bed, i could fit 2 more (so 4 total) under the port settee berth if i squeezed the flexible water tank (which is currently taking all.the space) into a smaller space by installing a partition under the settee.

This new location allows higher capacity but increases cable runs, so potentially bigger cables.

Being lazy, the aft cabin option is easier BUT I am concerned about havibg batteries in a sleeping cabin, despite that being the original location for the original (smaller) bank.

Thoughts?
 
I share your concern.
Very common to have batteries under the rear berths but on occasion you can smell them. The venting is not good.
Coded boats need top conform to the following:
8.4.2.3 would seem to apply unless your 12v charger is under 16Amp.
I wonder if this is why new boats come with a weak charger?

Batteries
8.4.1 Battery system requirements
8.4.1.1 Batteries and battery systems should be provided as indicated in Section 7.5.1, 7.5.2
and 16.2.6.
8.4.1.2 The battery terminals should be protected against accidental contact with metallic objects.
8.4.1.3 Battery charging systems should be fitted with circuitry to prevent overcharging.
8.4.1.4 A battery cut-out switch should be provided for all systems. It is preferred that this switch acts as an isolator, i.e. it is double pole, however, single pole is acceptable on the positive conductor. If a battery change-over switch is fitted and is provided with an “off” position, this may serve as the cut-out switch also.
8.4.1.5 Batteries supplying essential services (emergency lighting, steering systems, navigation and communications equipment) should be located in a position not likely to flood in normal operations or in the event of minor damage.Battery stowage
8.4.2.1 All batteries should be secured firmly to avoid movement when the vessel is subjected to sudden acceleration or deceleration, a large angle of heel, trim and in the case of sailing vessels, knockdown or inversion.
8.4.2.2 Where the maximum charging power output is less than 0.2 kW the batteries may be located in any suitable space without any special container requirements.
8.4.2.3 Where the maximum charging power output is between 0.2 and 2.0 kW the batteries should be located in the machinery space or other well-ventilated space in a box or locker.
8.4.2.4 Where the maximum charging power output exceeds 2 kW the batteries shall be placed in a suitably ventilated dedicated compartment within the vessel or a locker on the open deck, in either case stowage space is to be for batteries only.
8.4.3 Ventilation
8.4.3.1 To ensure that any evolved hydrogen is expelled, battery compartments, lockers and containers should be exhausted from the highest point of the space and air supplied at a level below the top of the batteries.
8.4.3.2 If mechanical means are employed to ventilate a battery compartment directly, then the components must not be a potential source of ignition. Reference should be made to the requirements of the ATEX Directive (EC Directive 94/9/EC concerned with equipment and protective systems intended for use in potentially explosive atmospheres).
 
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GrahamM376 said:
All our batteries are under the aft cabin double bunk, 560AH. Never smell them and the locker is vented to cabin.
Click to expand...

They should be in a battery box that is vented to the outside of the boat. Same installation as a gas bottle. Many acid batteries give off potentially explosive gases. That is why they need topping up with water. (hydrogen and oxygen)
 
theoldsalt said:
They should be in a battery box that is vented to the outside of the boat. Same installation as a gas bottle. Many acid batteries give off potentially explosive gases. That is why they need topping up with water. (hydrogen and oxygen)
Click to expand...

Maybe they should be but I bet that on 90% of boats they're not and I tend not to smoke in bed anyway:)
 
theoldsalt said:
They should be in a battery box that is vented to the outside of the boat. Same installation as a gas bottle.
Click to expand...

Point one - as long as they are well secured, there is no need for a battery box.

Point two - oxygen is not a problem. Hydrogen is, but is lighter than air, and will rise. Therefore it doesn't need the same installation as a gas bottle, the alkanes are heavier than air. A gas-style installation would trap hydrogen, not release it. In my view, as long as the batteries are not hermetically sealed in, hydrogen will be self-venting, by migrating through bunk or settee board bases (edges, finger holes, etc) to the atmosphere.
 
My batteries are in the same place. My thinking is that batteries only gas when they are being charged and people are only in the berth at night. We don't have a wind charger, only solar panels and shore-power. So when we're at anchor (which is most of the time when we're cruising) the batteries are not gassing when people are in that berth.
 
Interesting thread. Currently my batteries are at the bottom of the cockpit locker and a total pain to get to. My plan next winter is to move them under the quater bunk.
 
So far as I know, sealed batteries should not, in theory at least, vent hydrogen (or oxygen) to atmosphere. (Presumably, if the alternator or battery charger is functioning correctly). So, if you are using sealed batteries, you could in theory put them anywhere you like, although it would be prudent to make sure that any gases produced can vent to somewhere safe.

Conventional unsealed lead-acid batteries are, of course, another matter.

Hydrogen, incidentally, is not only lighter than air but also diffuses very readily, so it would actually be quite difficult to build a battery compartment which would keep the hydrogen in. Though I am sure it could be done! (and I understand has been done. Wasn't there an explosion in a boatyard recently from over-charged batteries, which wrecked the (fortunately unoccupied) boat?)

A cheap battery charger can give lots of volts (15 or more, maybe) in the final stages of charging. Which is a good argument for getting a better charger. Some smart chargers will use a substantial voltage at some stage in charging - someone else will know more than me about this; I am given to understand they shouldn't be used with sealed batteries.

Back to OP; in general, I suspect that lots of battery capacity is Good and even more battery capacity is Better.
 
Sailfree said:
Coded boats have to have sealed batteries. I assume these areless likely to "gassing" and releasing hydrogen?
Click to expand...

The blue guide on the MCA page doesn't state that, just that the battery box should be vented tot he outside. Has there been an update to this or is this requirement an extra requirement by some certifying authorities? Interested to know where this comes from as I have read this comment a few times now in other threads. :)

Thanks,

BlowingOldBoots
 
BlowingOldBoots said:
The blue guide on the MCA page doesn't state that, just that the battery box should be vented tot he outside. Has there been an update to this or is this requirement an extra requirement by some certifying authorities? Interested to know where this comes from as I have read this comment a few times now in other threads. :)

Thanks,

BlowingOldBoots
Click to expand...

See my post above
SCV 8.4.1.6
 
BlowingOldBoots said:
See my link from the MCA page http://www.dft.gov.uk/mca/blue.pdf Section 8.4.1 Which is clearly not the version you are quoting from. Do you have a link to your version please?
Click to expand...

http://www.dft.gov.uk/mca/mgn_280-2.pdf

Since you mention the blue code under the heading is this bit:

Notice to all Owners & Operators of Small Commercial Code Vessels; Boat Builders, Designers and Surveyors

This notice should be read in conjunction with the Blue, Yellow, Brown and Red Codes

And incidently, I agree with you. It's not in the blue code and I have seen charter boats with unsealed batteries. (Albeit a while back.)

So this is a result of harmonisation of several codes. Existing vessels are ok but newly coded vessels will have to comply.
 
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Ah! I had forgotten about that part, not being involved in this industry since 1989 it is now just of academic interest to me. I think I have made this omission before, oops. Thanks for the reminder.
 
Sailfree said:
Coded boats have to have sealed batteries. I assume these areless likely to "gassing" and releasing hydrogen?
Click to expand...
No they don't need to have sealed batteries. It is definitely not a normal coding requirement, unless something has recently changed. Venting any hydrogen is fairly easy and safe as it rises. Fitting a gas-bottle type bottom bottom drain is fairly pointless. Most new production boats have batteries under the aft berths, it makes for easy cable runs. Nothing wrong with any other position, but it costs more in heavy cable.
 
Personally, I think it might generally be better for the hydrogen generated to freely escape via the cabin than to be trapped in a box.
So unless the box is well ventilated, I think it is generally better unsealed.
It might be an issue when charging at high rates from shore power with the boat closed up.
As people put bigger battery banks and more powerful mains chargers on a boats, it is probably worth thinking about.

Sealed batteries will also vent hydrogen and oxygen if charged hard enough, e.g. if a cell fails short.

If you have a vent to the great outdoors, you want to be very sure seawater cannot get in, even in a big broach or pooping.

Why don't all batteries have fittings for a vent tube like motorbike batteries do?
 
jwilson said:
Fitting a gas-bottle type bottom bottom drain is fairly pointless. Most new production boats have batteries under the aft berths,
Click to expand...

I did not mean to imply that the vent should be at the bottom. Yes,of course, it should be at the top; mine is and the installation was original fitment by builder with a vent to the counter.

P.S. I have been present when a battery exploded which was caused by a spark igniting the gases. Something I never want to experience again.
 
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