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Old 10-12-2009, 05:16   #46
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notSURE, you really need to listen to your "betters" here. Virtually everything you said is wrong ( including the jumper cable nonsense).

Firstly you misunderstand 3 stage charging and your refernce to the charger website contains the greatest nonsense I have ever read on two and three stage chargers.

3 stage battery chargers , are firstly a constant current ( ie bulk). The charger raises the voltage until teh max current its capable of ( or set to) its transferred to the battery. Absorbsion,constant voltage, The charger holds the terminal voltage constant and the charge current is determined by the battery resistance, ( the charger doesent determine it persay). float is where the charger drops the terminal voltage so that the chrage current falls to a minimum level.

In general other then max and mix, chargers dont determine current flow as ohms law applies.

AGMs and Gells do NOT vent under normal charging conditions, venting removes battery capacity PERMENENTLY from gells and agms, both batterys recombine gasses under normal operation. Equalisation is not reccommened, and no charger that I am aware on the market has equalisation that cannot be disabled.

Secondly 3 stage chargers ( or 2 stage) despite what MR rowes nonsense says do not overcharge the batteries where there is a load, in fact they can undercharge. Look at the science, during bulk phase the battery accepts max current, if a load is there it merely slows the this charge phase.

Absorbsion phase, is normally controlled by sensing when the current falls below a minimim, if there is a load, then most smart chargers do two things, (a) they will return to bulk mode if the current is too high, ie the voltage will drop(b) most have a timer that prevents absorbsion mode going on forever. IN eitehr case voltage is never raised to cause gassing, especially with AGM s and gells setttings, usually the charger uses a lower absorbsion voltage for these batteries. ( to ensure that there is no gassing).

Very few production boats in my experience vent battery boxes to the outside, even with flodded lead acid. I have a boat with 12 such batteries in three bozes all vented to the interior. There is absolutly no degeration ( after 20 years to the plywood covers. The amounts of hydrogen given off is very small and will generally exit the boat in a short time.

BY all means ventilate your battery boxes, but please dont try and mislead us with "a little knowledge is a dangerous thing".
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Old 10-12-2009, 06:21   #47
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Originally Posted by goboatingnow View Post

Very few production boats in my experience vent battery boxes to the outside, even with flodded lead acid. I have a boat with 12 such batteries in three bozes all vented to the interior. There is absolutly no degeration ( after 20 years to the plywood covers. The amounts of hydrogen given off is very small and will generally exit the boat in a short time.

BY all means ventilate your battery boxes, but please dont try and mislead us with "a little knowledge is a dangerous thing".
Ok now my turn to disagree. Most production boats DO vent to the outside because most boats have their batteries in the engine space which of course is vented to the outside. It is the rare boat that has batteries in the living space mostly after market installations is what I see. ABYC and NFPA set these recommendations for a reason and just because something works on one persons boat does not make it the right thing to do.

I make my living inspecting boats and i have seen the damage caused by poor installations. The people who make these recommendations do so after long study it takes years in many cases. And we are talking explosive gases here. Yes under normal conditions you would never have a problem but I am the guy they call when things go wrong and they do go wrong.

Does not matter what type of battery you have it needs to be vented to the outside no if ands or butts, bring clean air in from the engine space if all else fails.

It sort of bugs me when people recommend doing something that is against current standards just because they have gotten away with it.

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Old 10-12-2009, 07:15   #48
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Ok now my turn to disagree. Most production boats DO vent to the outside because most boats have their batteries in the engine space which of course is vented to the outside.
I can give you the specific european experience and this is probably the largest manufacturers of production boats on the planet. For example Beneteau and Jeanneau do not specifically vent the batteries and they are not in the engine compartment, they are typically under the rear bunks. The battery compartment is not air tight neither to the accomadation or the engine bay, but EU RCD specs are against batteries being placed direclty in the engine compartment, though the starting battery often is.

Halberg rassy have also placed them in the rear cabin and bow thruster batteries under the forward bunk, nether are specifically vented to the outside

In my experience very few manufacturers place the domestic battery bank in the engine compartment,

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It sort of bugs me when people recommend doing something that is against current standards just because they have gotten away with it.
In my considerable experience most battery banks are not specificaly vented to the exterior. This would include at least my experience on 8-10 production boats types. This is despite ABYC etc


The reason is simple, unless you build airtight battery cases, which almost nobody does ( I dont any that do) Hydrogen rises so it will exit around teh typically unsealed edges of the box and collect near the underside of the deck where it will vent via the normal ventilators in most boats. Build up of hydrogen WILL not occur unless the boat is (a) competely airtight and (b) excessive overcharging of the batteries occurs. if you have an airtight boat , the least of your problems will be hydrogen!!!

Hence side venting of battery boxes is almost useless anyway and top venting is very difficult for batteries under bunks etc.

Again my main point was that agmS and gells do not vent under normal conditions, including fast charging, assuming proper termination systems are in place, ie IUU, IUI with charge limits or dv.dt termination schemes.
AGMS can actually take C/3 charging with gas generating without venting and will recombine the gasses.


The fact is that hydrogen buildup is only a concern in the battery box its not a concern for human life in the boat. ( with typical battery densities we see). Hence the issue is buildup in an airtight or near airtight battery box, with the possibility of explosion. vented into the accomadation area is fine. no buildup in the box and no risk to anybody, thats why most manufactuers dont build airtight boxes
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Old 10-12-2009, 08:20   #49
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I live in the USA and follow the recommendations of the US standards.

I have experience with 100s of production boats not just 8-10

We obviously disagree on this one and I am not likely to change your mind nor are you likely to change mine. I do however feel it is irresponsible to recommend to others to ignore the current safety standards. There are reasons for these standards I suggest if you think they are a waste of time you take that up with the originations that wrote them.

Like I say I have seen exploded batteries and I am here to tell you it is a mess, I would not want that in my living space. You seem to assume normal operating conditions which as we all know does not always happen. We need to plan for the abnormal as well. Things can and do go wrong.

We are both entitled to our opinions and that is what this forum is about sharing those opinions, I have presented my side and you yours we will let the readers decide what they are comfortable with, but I will stick with the published standards and hope others do as well.

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Old 10-12-2009, 08:28   #50
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Island Packet use to put them under the nav seat in the main salon with no venting at all. I am not sure if they have changed. My Shannon is in the pilothouse beneath the settee with a vent out into the room by the step and door to the outside.

Having said that there are always leaks to another compartment that can eventually get to the outside or the bilge area. I suspect that the air turnover just due to leaks in most of these compartments is high enough to avoid problems unless they have been intentionally sealed. That may be why most people don't see the problems described with the battery acid venting.

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Old 10-12-2009, 08:29   #51
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Just Curious!!--how many of you REALLY think your boat meets the relevent ventilation specs to which these valuable posts refer.

Avisor, Good question. I do not currently have a vent system but after reading the thread (even the menutia) I will be adding one to the battery bank in my seat locker. Just to keep dock lines, sponges and other assorted items intact.
I have the same reaction since one of our banks is in the sail locker !


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Old 10-12-2009, 09:11   #52
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but I will stick with the published standards and hope others do as well.
okay wise guy lets look at the ABYC "standards",

"E-10.7.10 A vent system or other means shall be provided to permit the discharge from the boat of hydrogen gas released by the battery. "

"Other means" basically means anything goes so an unsealed lid is sufficient. thats way manufacturers do so.

By the way I inspected many 100;s of boats would you care to mentioned specific models like I have that have specific battery compartment venting to the outside. List them

Quote:
like I say I have seen exploded batteries and I am here to tell you it is a mess, I would not want that in my living space. You seem to assume normal operating conditions which as we all know does not always happen. We need to plan for the abnormal as well. Things can and do go wrong.
You dont understand what the "standard" and what we are talking about here is about, build up of hydrogen gases in a battery box and the need for vents has nothing to do with "exploding batteries". I too have seen this , exploding batteries are due to thermal runaway and very few commercial installations have boxes that would contain a major battery explosion, This has nothing to do with hydrogen buildup.

Venting is to enable the release of small quanties of hydrogen gass given off from the charging process so tha these do not build up in the battery compartment, Thats nothing to do with exploding batteries, which is caused by a buildup of pressure inside the case.

I say again

simply allowing the battery box to vent into the acomadation space and then allowing the gas to exit using normal boat ventilation schemes meets teh requirements, is perfectly safe and is what the vast majority of manufacturers do.

You sir have provided no hard facts to the contary.
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Old 10-12-2009, 09:41   #53
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goboatingnow: ask some chemist for a strip of litmus paper. Set it atop your battery. Inspect it from time to time. Then ask yourself, "How did it change color?" It's a simple enough proof that there is not evidence of acid vapor escaping the cells. If it does escape, unlike hydrogen that flashes off quickly, the acid gets absorbed into whatever porous material it can find: fabric, foam rubber, wood, and even lung tissue. That's why folks use the phrase "litmus test" for a yes or no answer to the evidence of something. If you don't have it change color, there is no danger of acid vapor. If it does, then you might be wise to consider venting. Then we can all get on to more weighty discussions.
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Old 10-12-2009, 09:45   #54
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We have a couple very knowledgeable members here with good advice and explanations...I have personally learned from both sides of this issue and I want to personally thank both of you.

The explanations on how a step charger actually works was very enlightening to me as well.

FWIW ..to all interested...I have explodes two batteries in my life with jumper cables..fortunately I have not been injured but I'm not so cavalier with them anymore...still jump many of them annually just aware of the potential and try to shield myself..
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Old 10-12-2009, 11:15   #55
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We have a couple very knowledgeable members here with good advice and explanations...I have personally learned from both sides of this issue and I want to personally thank both of you.

The explanations on how a step charger actually works was very enlightening to me as well.

FWIW ..to all interested...I have explodes two batteries in my life with jumper cables..fortunately I have not been injured but I'm not so cavalier with them anymore...still jump many of them annually just aware of the potential and try to shield myself..
If you don't mind....I'm interested in how specifically you blew up two batteries so that I can attempt to avoid the exact behavior that led to the explosion(s), whether by 'jumping' with cables or charging with a charger.
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Old 10-12-2009, 21:33   #56
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I would like to find out how to set up a relay switch to turn my battery ventilator fan on ONLY when I'm charging. That would really save me some electrons.

As I will be returning to working on my own boat, shortly, I can start sending pictures of the battery box and ventilation system project that got interrupted by the intervention of several months of seven day work days. I am installing four L-16 six volt batteries in series parallel in the bilge of my multihull. The vent is sort of like a dorade, but with snorkle valves and one-way flap doors. It's too weird to describe, so you'll have to wait for the photos. But first, some sanding, paint and hardware to make it entertaining.
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Old 10-12-2009, 22:30   #57
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If you don't mind....I'm interested in how specifically you blew up two batteries so that I can attempt to avoid the exact behavior that led to the explosion(s), whether by 'jumping' with cables or charging with a charger.
I have a lot of heavy equipment so I have quite a few batteries around here to maintain..less now then when it was all out on jobs with 7 employees but I still have most everything it just sits a lot now so I remove some of the battries.

Several years ago we were on a good sized job and one excavator had a bad battery and was needing a jump every morning..we thought we were to busy to deal with it proper so every morning for a few days I would just pull up to it with the service truck and jump it with the welder we carried on board...took all of 5 min...it was a 24v system and the DC welder puts out about 28 to 30v and your selection choice of amperage up to 235 which I always used about 150 to jump..on about the 3th day I didn't make good connection with the cables and when my operator hit the key after about 5 min of quick charge and hydrogen build up she arced on the positive post melting it completely to a nub and blew half the side out of one of the batteries.

The second one I blew was in one of our Voyager vans...I always use to hook up the hot battery and give the jumpers loose ends a good quick strike together to make sure I had a good connection before hooking up the battery to be jumped ( How many times I have thought i was charging a battery only to find out I had a poor connection to the hot battery bascily doing nothing for 30 min is what lead me to this erroneous practice ) well there was in addition to this a small 75 amp booster charger that just was not giving quite enough ummph so I was doubling up the two ..only problem is the charger had been running for 15 min and the bat was already gassing so all it needed was a nice spark to do its thing and I gave it that when hooking up the jumpers..I was lucky that it blew toward the firewall and not toward me as acid did spray.

Some where in this forum or in another I have shared several of my episodes with batteries and battery cables and terminals over the years...I feel I am qualified to some extent to warn others about the shear power and heat batteries can develop..I have melted several posts right off of batteries from poor connections due to vibration loosing them up and one morning you hit the key and there is the sound of bacon frying and you know instantly what just happened both the cable end and battery post are gone.

There is a welder we use in the field that with 3 combined batteries in series forming 36v will put out 600 amps and can weld 1" plate in one pass...don't underestimate the power or danger of your batteries like I did for 20 years...they are not time bombs waiting to go off... but they can and do explode if conditions are right...Like gasoline its safe until its not so just slow down and take due diligence and you will more then likely never have an issue..be cavalier like I was and its just a matter of time.

Im no more affraid of battries today then I was before I blew my first one just smarter in the way I handel them.

Hope this helps someone.
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Old 10-12-2009, 23:08   #58
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Very interesting discussion.
On my E40, the PO had wet cell golf cart batteries in the engine space, mounted in plywood boxes, 4 below, and 4 above. You had to remove the 4 above to access the lower bank... and in the engine space as well, where heat, vibration... not good.
I have since replaced them with TPPL AGM's, 600 AH, mounted below the master bunk. I have not mounted them in boxes, only secured them. They are charged via a victron inverter charger and a balmar max charge. both set for agm's.
I do not anticipate them off gassing, but know that they "COULD" if improperly charged. The space is open to the head via a cut thru, and the head is vented via a nicro solar vent. So, indirectly the space is ventilated. I will be checking the space often to see if any problems develop from this install. I do not anticipate any. But the autopilot is there, and the steering quadrent. Not much else.
In the many boats I have looked and and the few I have had surveyed, not one that I could remember had any specific venting system. Most boats have batteries placed where ever they can be placed. And few manufactors have extended cruising in mind when they build their boats. Most boats come with one small house battery and one start battery. They are placed in areas that can not easily vent to the outside. Mounting batteries in a engine space is a recipie for early death and poor performance IMO.
No matter where you place them, or in what box, if you out gass them, they will vent corrosive fumes, so use hydro caps for wet cells, and do not go beyound the parameters for gell and agm.
Lithiums are a different story I believe, and the technology is pretty exciting. In 10 years time the cost will be better and well will maybe not be having this discussion. But in the meantime it is good to debate the issue.
I learn much from them.

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Old 10-12-2009, 23:51   #59
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Question for all you folks who report knowledge of so many production boats:

Can you give us the manufacturer and model data for ANY production boat from anywhere in the world that has actively vented battery boxes... ie using a powered fan of some sort leading to the exterior of the boat, as reccomended earlier in this very interesting thread?

My experience numbers are not nearly as grand, but I can say with some certainty that I have not encountered even one such.

Cheers,

Jim and Ann s/v Insatiable II
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Old 11-12-2009, 05:56   #60
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This works well to control a fan when charging: Catalog Frame
Scroll down for "Battery Ventilator Controller".

Charlie
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