Battery box designs

[mjt]

Hi all.

Battery boxes are supposed to:

1. Stop leakage of the battery contents,

2. Provide an air bubble in case of sea water flooding to give batteries a chance to stay alive and avoid production of dangerous gases such as chlorine,

3. Be externally vented to avoid buildup of explosive hydrogen, and

4. Hold the batteries in place (including worst case, capsize).

The battery boxes I see for sale seem to have ventilation holes in the top cover, making them useless for requirement 2 and also for requirement 3 in an enclosed cabin (a typical yacht).

How does your boat go about providing a battery box or storage compartment resolving these potentially conflicting (2 and 3 especially) requirements?

[cooper]

1. yes


2. Shouldnt they be mounted high enough to stop water ingress or at least have one battery that is high enough to keep vital services going (The height that once its reached you would probably be "stepping up" into a life raft.)

3. Do they really have to be externally (as in outside the boat) vented ? Wouldnt a vent into the main area of the cabin etc be enough to disperse the gasses to a degree suficient to stop an explosion from happening ?


4. With holes in the top and an inverted boat you are going to have a lot of battery acid sloshing about. (Go with gell batteries ?)

[mjt]

Originally Posted by cooper

2. Shouldnt they be mounted high enough to stop water ingress or at least have one battery that is high enough to keep vital services going (The height that once its reached you would probably be "stepping up" into a life raft.)

Sounds like a good idea, but I haven't seen a yacht with such an arrangement yet. I suppose people want to keep heavy batteries as low as possible (without exposing them to the bilge environment) for stability.

Originally Posted by cooper

3. Do they really have to be externally (as in outside the boat) vented ? Wouldnt a vent into the main area of the cabin etc be enough to disperse the gasses to a degree suficient to stop an explosion from happening ?

My understanding is that you should externally vent because the cabin is where naked flames and sparks occur (stoves for instance).

I've never actually seen an externally vented battery on a yacht and so I would like to know how people do it without the risk of sea water flooding back down the vent into their battery box/storage compartment.

Originally Posted by cooper

4. With holes in the top and an inverted boat you are going to have a lot of battery acid sloshing about. (Go with gell batteries ?)

Yes, it sounds like AGM or Gel are the way to go safety wise.

So how do you store/vent your batteries in your two boats? (I'm looking for design ideas as I am thinking of rearranging my batteries.)

[Pblais]

You won't be sealing flood lead acid batteries in a capsize and venting them properly. If you use AGM batteries than all you need to do is just secure them as that is the only thing they do require other than proper charging. AGM's are the best for boating. I switched to them ii the prior boat and loved them but have not switched yet in the new boat as the whole charging system will require replacement. The charging system has to be set properly for one or the other else it's money wasted.

Flood batteries will out gas and that will include Sulfur Dioxide as well as Hydrogen Sulfide. Pure hydrogen also is possible. The out gas is a corrosive mixture and is what needs venting else any non Nobel metals will show signs of corrosion. On the last boat the PO put the A/C unit in the same compartment. The aluminum heat exchanger was corroding when I got the boat. Not fatal but could have headed in that direction.

The battery box is more for the overflow that can happen when the batteries boil from poor charging. Not that it is normal to happen but because it could happen even on a proper boat should you not monitor the water levels in the cells. You want to contain the spill no matter what.

In the case of a capsize your electrical system has but a short lifespan. The salt water and the electricity will quickly destroy anything with current in it. Putting batteries inside something won't help all of that much. The bigger danger is that they come loose and a 70 lb battery flying loose could put some nice sized dents in your skull. In a capsize you would expect all heck to break loose and violent motions can make deadly weapons of even small objects. A battery could smash through a bulkhead with enough force launching it.

[Paul L]

I'm not sure I agree with the logic here, but it sounds like ABYC still requires a battery box for AGMs. Not sure if an insurancxe survey in the US would get past this:

Q. ABYC E-10 requires that I have a 12" "Dielectric shield" above my battery for the purposes of gassing. I understand this requirement when installing traditional "Lead Acid" type batteries, however, I am installing gel-type batteries and do not see the need for this spacing.

A. First, E-10 does not differentiate between traditional (lead-acid) and newer types of batteries (gel) that minimize or eliminate hydrogen gassing. Keep in mind that a battery is not permanent. At some point in time, the unit will have to be replaced. Generally these batteries are replaced with what the owner can afford or what the owner finds is available at the time. The suggested method of installation found in E-10 takes into account this common situation. Since hydrogen gassing can affect most materials used in component construction (e.g. aluminum cases on chargers/inverters, fuel lines) the standard calls for the 12" of dielectric shielding.

Paul L

[mjt]

Originally Posted by Paul L

ABYC E-10 requires that I have a 12" "Dielectric shield" above my battery for the purposes of gassing.


...<snip> ...

Keep in mind that a battery is not permanent. At some point in time, the unit will have to be replaced. Generally these batteries are replaced with what the owner can afford or what the owner finds is available at the time. The suggested method of installation found in E-10 takes into account this common situation. Since hydrogen gassing can affect most materials used in component construction (e.g. aluminum cases on chargers/inverters, fuel lines) the standard calls for the 12" of dielectric shielding.

This sounds to me like a common sense approach. From what I have seen in yachts around the place, people tend to be lazy when it comes to batteries.

Do you know what they mean by '12" Dielectric shield'?

[GordMay]

Goto:
http://www.cruisersforum.com/gallery...p?i=3206&c=500

[mjt]

Originally Posted by GordMay

Goto:
http://www.cruisersforum.com/gallery...p?i=3206&c=500

Thanks Gord. That's a factor I hadn't considered - apparently to protect fuel system components from arcing.

[mjt]

Originally Posted by Pblais

You won't be sealing flood lead acid batteries in a capsize and venting them properly.

My thoughts exactly, hence my question to find out what sort of balance most people arrive at. It sounds to me like AGM batteries resolve some of the problems.

Originally Posted by Pblais

If you use AGM batteries...

<snip lots of useful info - thanks Paul>

In the case of a capsize your electrical system has but a short lifespan. The salt water and the electricity will quickly destroy anything with current in it. Putting batteries inside something won't help all of that much....

I suppose the hope is that the boat will right before the air bubble in the battery box is flushed out with sea water, giving you some chance of electrical recovery. Apart from upsetting the battery chemistry of a flooded cell, you probably don't want sea water to short circuit the batteries either.

So how is your battery storage system arranged? Is it vented externally?