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Old 07-01-2010, 16:28   #1
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Battery Off-Gassing?

Hello,
This is my first post to this forum. Thanks, in advance, for your help.

Our boat is a 36-foot Rival. The house bank consists of two dual purpose 12-volt batteries from West Marine (Sea Volt Dual Purpose 745) purchased 6 years ago. They sit in a box that also serves as the seat for the navigation station. Here is a picture of the batteries in the seat:

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The box is ventilated by five holes on the front side. About a year ago I noticed a dark stain forming around the five holes. This has gotten darker and larger in area since then. Here are two pictures of the stain:

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The stain is only affecting the exterior woodwork of the box (or seat) -- there is no stain on the inside of the box. I believe the woodwork is teak.

It appears that whatever the holes are ventillating (hydrogen gas?) is staining the woodwork. Is this right? And if so, are the batteries producing too much gas? If they are, why and what's the best fix?

Thanks to any and all who might shed some light on this problem.

zhdad
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Old 07-01-2010, 17:02   #2
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There was a pretty good discussion about venting battery boxes not long ago. You should do a search for that and read that discussion. And you are showing exactly why ABYC recommends battery boxes be vented to the exterior of the boat not the interior. Those stains are the result of poisonous gases. Batteries do gas of when charging. your best choice would be to vent the box overboard, maybe through the engine compartment.

Good Luck
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Old 07-01-2010, 18:41   #3
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no theres something abnormal going on here, IF this only started a year or two ago , I presume the rivals a good few years old. I wonder if your severely overcharging your bank. Actually this is a good system better then "external venting" which nobody does anyway, As atleast you are getting a warning of a problem,

as to the sugestion to vent it into the engine compartment, sure its only hydrogen, ( remeber the hindenberg).

btw you boat meets the requirements of the ABYC standard.
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Old 07-01-2010, 18:41   #4
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The off gassing of batteries is the breakdown of the water into hydrogen and oxygen. The hydrogen, being lighter than air, will escape to the outside eventually. It's only a problem if trapped in a small, confined area as it's highly flammable, remember the Hindenberg. The best way to tell if the batteries are being overcharged is how often you need to add water. I normally get at least 3 months and more like 6 months out of a top-off.

I don't know what would be causing the staining of the woodwork though it's undoubtedly something to do with some other gas coming off the batteries. I've had batteries sitting next to an untreated wood wall for many years for our house PV system. They never stained the wood even when the batteries got overcharged to the point of blowing the tops off.
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Old 07-01-2010, 20:24   #5
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I will check out the previous thread on venting -- thanks for that note.

I agree with goboatingnow that there is something weird going on here. The boat is an '85, and the stain is definitely within the last year or two, so it seems to be something to do with these particular batteries (i.e., previous batteries did not cause a problem with this ventilation system). Perhaps the current batteries are faulty, or old (is 6 years old?). I had considered the overcharging issue, but we are not having to top off any more frequently than I would expect. What other gas might come off batteries?
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Old 07-01-2010, 22:00   #6
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Well, the earlier battery venting thread was very interesting. Here it is:

Ventilation of Battery Compartment

In relation to my problem, two questions emerged:

- should I just change to AGM's or Gell Cells? (and why doesn't everyone have these instead of flooded cell if indeed they don't vent bad gasses?)

- what the bleep is sulfuric acid vapor and how do I know if THAT's what is messing with my woodwork? Sounds like dangerous stuff.

One additional observation. The ventilation holes that are developing a stain are at the bottom of the battery box. At some later date another ventilation hole was added to the top of the box -- it appears to just vent into the cabin via an open space under the quarterberth. If hydrogen gas collects at the top of the box, then it's the newer hole -- not the old holes at the bottom -- that are going to the gas out. If that's so, then what's staining the wood around the holes at the bottom?

Thanks to anyone who finds this interesting enough to comment on.
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Old 07-01-2010, 22:07   #7
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ahh, this has nothing to do with hydrogen gas, as I said in the other thread gas discharges from non sealed LA batteries does not in my experience cause any noticable damage for if it was thousands of production boats would be affected.

I suspect you are having battery acid spills /leaks, you could be boiling the batteries, excessive overcharging can cause the leaking of the electrolyte, this would definity discolour the varnish, which is what I suspect is being attacked here.

battery comparments should NOT have low level vents for that very reason.
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Old 08-01-2010, 10:22   #8
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If your batteries are six years old, they are nearing the end of their lives. Getting much over 4 years in a demanding marine environment is a blessing. I'd change them out just because of the age if I was going cruising or in a situation where I would really need to depend on them.

This website has good information on battery types: Deep Cycle Battery FAQ

The answer to your question on why everyone doesn't go Gel Cell or AGM is a combination of money and performance. Lead Acid batteries are about half the cost of the more advanced batteries and last just as long with a little maintenance.

Gel Cells are extremely finicky about proper charging and can be ruined by one charging screw up. In my view, they are just too fragile for life or death marine use.

AGM's may be more robust but the cost is a killer. AGM's do have some advantages like higher charging rates for alternator or gen set charging with a high tech, read expensive, charge controller. Charging via solar arrays is probably no more efficient than lead acid. If you are one of those jerks that loves to disturb quiet anchorages running your gen set to keep up with your profligate use of electrons, AGMs may make you a less hated harbor mate.

Still don't know what's causing the discoloration though acid contamination seems the most likely. Be careful if it is 'cause it will eventually cause the plywood to delaminate.

FWIW, there are battery caps that cut down on water loss from batteries. There are two varieties, one uses a chemical reaction to recombine the oxygen and hydrogen back into dioxyhydrogen and cut water loss to a minimum. Unfortunately, these can have serious side effects, like explosion, if the batteries are not charged according to cap requirements. The other type use a mechanical trap to keep the gases from escaping and a less efficient recombination of the H and O. I've used the second type for years with success but they don't eliminate maintenance and regular checks.
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Old 08-01-2010, 10:31   #9
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Change position red lead!

Quote:
Originally Posted by zhdad View Post
Hello,
This is my first post to this forum. Thanks, in advance, for your help.



Attachment 12446

zhdad

Hi.

Outside of the discussion on the venting noticed in this picture that you have your insulated red positive lead passing by and touching both negative terminals.

I would route this away from the other leads and terminals. A little vibration some ware on the insulation and bang!

This has nothing to do with your question but seriously look at this today..

S
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Old 08-01-2010, 15:00   #10
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If it were not a battery box, I think comments may have gone in a very different direction.

What you know:
1. The batteries are six years old.
2. The problem started about a year ago.
3. The stain only appears on the outside of the box.

Scale is really hard in a picture and these look almost "oily" instead of wet. I am curious how long it took to get to the current size (and how big that size is). Is it wet or does it feel oily?


I suggest trying the following:
- Pop one or all of the vents out if you can. They look to be wood with a screen. Looking at them (I had to enlarge the picture - good job with them) they seen blocked with something (wax? Lint?). Start by clearing them so the screens are wide open.
- If the vents are single piece units, and feel "cool to the touch" they may be acting as a sink for condensation. It could be the boat was moved to a different location, air flow changed within. Perhaps the boat is not as used as before or new ports were put in or insulation? Something to change air flow?
- Look at the hole where the vent was. Is it swelling across the entire thickness of the board or only the front edge? If it is the front edge, it seems that again condensation may be playing more of a role on the surface or just behind the front edge of the vent.
- Next pull the batteries and look for anything running through the tray. Are they leaching anything?
- Does the tray have a drain? If so, pull the tray. That will show you everything.

Finally, in the last year or so have you changed wood cleaning products? The collars around the vents are a perfect area where people (myself included) may tend to spray more and wipe less.
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Old 09-01-2010, 10:12   #11
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Thanks roverhi for the information on battery types. And solitude, for the heads up - not sure why it was installed like that, but looks like I can reshape it easily enough.

Kefaa, I don't think it's a condensation issue, mostly because I don't see anything similar elsewhere in the cabin, and there are a lot of finger holes constructed the same as these ventilation holes. You're right, though, that it's time to just the pull the batteries and look more closely at the box and the holes and the stain. It appears that that there was a leak of some sort at some time because I now see a crumbly white-grey residue on the inside walls of the box from the floor up to about 3 inches -- just above the level of the holes. This residue is visible if you zoom in on the lower left-hand corner of the first photo I included with my post. This suggests that there was a single event (a leak? a "boiling" over?), and as much could account for the stain appearing more or less suddenly (this is hard to guage since it could have been there for awhile before I noticed it, and before about a year ago I wasnt' principally responsible for the boat and its maintenance). Points counter to this theory are: the exterior surfaces of the batteries, from what I can see, are clean; if there was a "leak" wouldn't it be continuing, even worsening; and if there was an event like this, my dad (who managed the boat previously) would surely have noticed!

Ok, so there are some thoughts. I'll pull the batteries and see if there's more to learn. As per roverhi, might be time to replace them anyway.
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Old 09-01-2010, 16:58   #12
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Mystery solved, sort of

Just to conclude this tale...

I did pull the batteries and things were as I thought -- there had been a spill or a leaking of something that had left a residue on the bottom of the box and up the inside walls. The inside is coated in fiberglass so it is fine, but the liquid (with its corrosive material, presumably acid) was able to reach the little vent holes and enter into the nice interior woodwork. I cleaned everything with a baking powder solution, including the stain, and rinsed and dried.

The batteries had no evidence of having leaked in any way. This means the "spill" event happened prior to those batteries being installed. Neither my dad nor I remembered having seen the stain before (and truthfully, it's not in a very visible spot), but -- who else? -- mom did. As she noted, her spot at the saloon table gives her a pretty good view of it.

So, two lessons learned. 1) Don't assume that something has just happened simply because you just noticed it; and 2) Always ask your mom.

Thanks for all the help and insight. Solitude, I would show you the new red lead configuration, but forgot my camera today. Thanks.

zhdad
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