Am i being a div?

rogerball0

rogerball0

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My attentions turning to the battery compartment as i will begin building out that part of the boat soon Am i being a bit thick in thinking if the batteries i put on board my boat are sealed 'leisure' types and say a red flash battery for starting purposes - also sealed - do i still need to vent the compartment?

The area for batteries and electrics (below) will have the batteries sat in a compartment in the bilge, directly above (separated by a removable top) will be electrical panel, wiring gubbins etc all be it in cabinets, is this sound? Just thinking about the lightness and flammability of Hydrogen hence the question about venting seeing as it shouldn't escape 'cos they're sealed.

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Thanks in advance

Roger
 
My only thought is while it's good to have weight low down, do you want all your power that low?

I'm thinking what happens if you get a leak - you want the bilge pump to run for as long as it can and it won't if the batteries are underwater.
 
LIB, could put a sticker in compartment saying to use sealed only although i'm quite sure this boat won't be leaving my family anytime soon but i guess it wouldn't hurt to run a pipe off the top of the battery box to the outside.

Good point Dylan, can't think of any off the top of my head.

Phil M, Having power that low - didn't think about it really as i'm trying to counter balance with additional tanks on the other side of the boat.

Thanks for suggestions, keep 'em coming. It should be said my family would probably answer 'yes' to the question posed for a multitude of reasons & not necessarily boat-related.:D
 
I suggest vented, not because of fire but for ambiance. Sealed compartments mostly aren't compleately sealed and can suffer from mold or mildew. A chimney style vent would help keep the water out if the boat is flooding.
You should also include a tie down bar or strap so the batteries can't move around.
 
You say "sealed leisure". I suspect you mean "sealed for life maintenance free". If so those are flooded batteries and they do gas, it's just that they have enough electrolyte to last their lifetime without topping up, usually the small print will limit the charging voltage to about 14V. If you use significantly higher voltage than that, they will gas a lot more and may run out of water.
With this type strictly speaking you should vent the compartment, although modern batteries gas a lot less than used to be the norm.

If you do actually mean "sealed lead acid" or "AGM", correctly known as VRLA (the Red Flash is of this type) then in theory you don't need to vent. However if your charger goes wrong and puts too many volts on, they will gas.

The only really safe answer is yes, vent the compartment, but unless you are having huge batteries and a big aggressive charger, the risk is minimal.
A worse problem used to be batteries emitting acid spray if boost charged but that doesn't really happen with modern ones (unless you have accessible vent plugs and remove them when boost charging, as used to be common practice.)
Of course unlike LPG, vented gas is not heavier than air and will disperse not settle in the bilge.
 
My batteries tend to get warm due to being in a moulded box surrounded with polyurethane foam, with bunk upholstery on top. In the past I have boiled them on long motoring trips. To try to reduce this possibility I added a fan blowing through the box, air exiting into the tunnel aft of the gearbox. The batteries shown are older wet cell ones but my current ones are sealed.
Batteryboxfan.jpg
 
dylanwinter said:
mine have always been in unvented lockers

I am still here to post on this thread

has anyone on here got first hand experience of a fire caused by a yacht battery?
Click to expand...

Yes!
June 18th 2013 Messolonghi.


The entire topsides of the boat, which had just been put in, caught and burnt out.
In that case a sealed engine-start battery in the engine compartment caught fire.

I've had a battery, with a faulty cell, reach 86C, under the influence of the smart charger. That in Rethymno in August this year.
There's plenty of research available on runaway thermal effects on lead-acid batteries.
 
rogerball0 said:
Vented it is then, never thought about using PC fans i guess i could whack one down low in the bilge drawing air into the box and set one in a pipe (40mm) exhausting to the outside, i guess it wouldn't draw much current.
Click to expand...

Computer fans typically draw around 0.1 to 0.2A, depending on size. They're usually very reliable. I use them to aid air circulation around the fridge coils and the bowthuster motor.
It'd be simple enough to put a thermal switch in the circuit so it only runs when the compartment gets warm. They can be had for a couple of squid.
 
Roger, if you fit a fan it might be a good idea to have the fan "pushing" air into the locker (as shown in Vyv Cox's post) rather than have it pulling air and battery gases out past its electrical contacts.
 
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