Battery Outgassing

As per Lyn's response, go with the VRLA Deep cycle batteries.

Regards,
Sapper

As the other respondents have suggested, VRLA batteries will work. They are more commonly known as "gel cell" batteries. They can be placed anywhere and are commonly used in home security systems and commercial fire alarm panels. They are however more expensive. They are maintenance free and will work much better (last longer) if trickle charged.

If you have a vent hose already hopefully on the top of the box.

Place some vent holes or a hose on the bottom of the box, the dangerous gas will rise and fresh air will take its place.

No reason why this should be dangerous. It is a lot cheaper than Gel cells.

Garth,

What you say is true for wet cells, but he wants to increase capacity as well, so he needs to eliminate the box to get more cell in the "Loop".

Regards,
Sapper

Hydrogen goes straight up. It doesn't hang about long. Just ventilate.

As usual, people treat accumulations of Hydrogen as "unimportant". Nothing could be farther from the truth, even small accumulations of Hydrogen gas can have dangerous effects.

Every year many are completely blinded by such explosions....See here:-

http://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery

Where a "good" example of the powers produced can be seen here:-

You need either to vent using explosion proof ventilators ( for boats is a good sourcing area) that are activated each time you connect to shore power.

There are also SLA (Sealed Lead Acid), but if overcharged, they will eventually blow off gas via a pressure release valve.

I am not a Gel battery user, but they sound good and others have already mentioned them, have a look here:-

http://en.wikipedia.org/wiki/VRLA_battery

Take care and observe all safety precautions properly, not forgetting an "Danger Explosion" Label on the final result!

Nice picture. But the problem is not hydrogen accumulation in the battery compartment, the problem is build up within the battery housing accompanied by an ignition source, usually a spark during a "jump-start" of the vehicle.

A few things. Keep your terminals clean and TIGHT. I would go for the GC2 deep cycle batteries you can buy from Sam's Club for about 80 bucks a pop. (no pun intended ) These are golf cart batteries, hence the GC2 designation. These batteries give you the best W-hr/$ deal in the industry because they sell gazillions of the things.

The old-style vent caps on these batteries readily dissipate any hydrogen evolved during the charging process. Buy a polyethylene battery box and put a flex hose vent or two to the outdoors. There is little need for active venting systems (i.e. fans) because hydrogen is notoriously difficult to contain. Hydrogen has the highest diffusion rates of any gas and it dissipates very quickly in air. The lower explosive limit for hydrogen is about 4%. Interestingly enough, the upper explosive limit for hydrogen is 96%. In fact, larger the battery compartment the better.

My dad gave me a couple of GC2's that he used for a few years on his boat in 2004. We put them on our frequently used travel trailer for house batteries. With reasonably poor care, we are just now in need of replacing them. Keep the water level above the plates but avoid the temptation to "fill them up" to the upper limits because you lose more acid this way by bubbling through the vent holes in the caps and that makes a mess.

No need to freak when dealing with batteries, but think your situation through and determine where your risks are and how to mitigate them.

You are forgetting basic Chemistry (not that I was all that good myself), the gas produced is not "just" hydrogen, it is a mixture of oxygen and hydrogen!! What the Germans call "Knallgas".

"Knall" is an explosion......

Due to the mixing of the two, it makes the end result VERY dangerous..........no extra air is actually needed for a good big bang.......only to allow the possible victim to breathe.....

The following text is taken from the first weblink:-

Lead-acid batteries contain a diluted sulfuric acid electrolyte, which is a highly corrosive poison and will produce flammable and toxic gasses when recharged and explode if ignited.

According to PREVENT BLINDNESS AMERICA, in 2003 nearly 6,000 U.S. motorists suffered serious eye injuries from working around car batteries. The U.S. Eye Injury Registry reports that it is the third leading cause of eye injuries at home.

When working with batteries, you need to wear glasses (or preferably Z-87 rated safety goggles), have plenty of ventilation, remove your jewelry, and exercise caution. Do NOT allow battery electrolyte to mix with salt water. Even small quantities of this combination will produce chlorine gas that can KILL you!

http://electronicsbus.com/lead-acid-battery-explosion/

http://www.wisconsin.edu/oslp/em/compliance/battery_leadacid.htm

http://www.ehow.com/info_8139940_dangers-lead-acid-batteries.html

These websites tend to disagree with your level of knowledge and advice on Battery gas. Also there are many more sites warning about such injuries.

So you yourself have been lucky up to now.......

Yes they do evolve both hydrogen and oxygen. The oxygen already exists in the battery housing anyways. I am very familiar with the chemistry having worked with a 1.2 MW-hr silver-zinc battery. The electrolyte is KOH. Those also will evolve both hydrogen and oxygen during the charging process. For charging these batteries an air flow is maintained during the charging process and then at the end of a charge, a nitrogen blanket is applied to the housings. They do evolve some H2 and O2 during the discharge process but at very low levels. O2 sensors and combustible gas sensors monitor the atmosphere. The main difference is that these batteries were installed in titanium housings with a "free space volume" of about 5-10% of the total volume. The confined spaces is what gives the greatest concern.

Again, the problem is confining the gases to the battery housing. With properly vented battery housings this is a non-issue. I'm not saying there aren't problems because there are. In spite of all the "training" many people have not a clue as to the proper methods of jump starting a car, hence the injuries. My dad luckily escaped injury from a battery explosion when he was a young man jump starting a car. He made sure every one us in the family knew the exact procedure to jump start a car.

Of course these websites will disagree. Just look at how risk averse our society has become. It's all about avoiding risk at almost any cost, not about managing risks. The lawyers have run rough-shod over society filling their pockets at our expense. Ultimately, those with the money are forced into extremely conservative positions for fear of being sued. Just try to find a swing set at school playground anymore. We're not teaching our kids anything about managing risks.

Luck plays no part in it, knowledge and situational awareness does.

Sorry, I cannot agree. Managing such risks as a LA battery can possibly give, means having to make sure that nothing happens, your management scheme seems to agree that an explosion in 50% of the installations is a good average......or even in 10%, but even 1% is too much, not that we will get much below that at the best of times, but we can hope.....

The only good average is when NO explosions occur.....you either get it right first time, or there is a risk, and believe me, having a pond or two of lead, intermingled with plastic, covered in a Sulphuric acid sauce blasted into your face will make anyone a(n eye) loser.....

I am sure that your Dad would heartily agree......you either do it right or take the possible consequences......

Nobody here (least of all me) is saying here that ignoring some safety rules (risk management?) will produce a 100% failure scenario, but why bet on such a result either way?

Where is the gain from NOT doing a proper job? I fail to follow the reasoning, especially after you describe (in a totally accurate manner I am sure) what precautions you took with certain battery types......though some might say that was at least 101% or more safe........but still totally correct.

In the USA in 2003 (if I remember correctly), some 6000 people suffered injuries from batteries, that's far too many.....

Wishing you a great day (and having and retaining both eyes!)

I thought the reason I asked was that I AM concerned about the possible hazards related to the accumulation of hydrogen gas. The existing battery box is next to the aux power plant, thus an ignition source, so I want to err on the side of safety. I admit that is not unusual for me. I probably am a bit too "Don't sweat the small stuff", but having seen several battery explosions, not to mention the film of the Hindenburg, I want my family to be safe so I am worrying about this one. -- JHF

Don't worry - every forum has got one.

Another option on 'type of battery' is lithium ion (Lion) these have a high energy density and are quite light. Far less mass to haul than lead acid equivalent storage and would likely give the increased capacity you seek within the current volume allocated - depending on cells chosen and dimensions existing.

You do need to change your charger to a compatible type.

They are a little pricey but cost is falling with the EV use rising. You might even pick up the whole system at a wreckers.

Circuit breaker you wrote:

"The current battery is a group 24 wet cell deep cycle in an airtight enclosure with a vent hose to the outside. A larger battery will not fit in the enclosure. Is there a battery that will not present the problem of hydrogen accumulation?"

You also indicate that "the existing battery box is next to the aux power plant, thus an ignition source, so I want to err on the side of safety".

You have a fundamental redesign issue to deal with. Most Travel trailer and RV builders are not experts on battery charging and compartment design. With an aux. power plant right next to it your options to change the compartment volume is very limited. Group 24 is a small battery and evidently not intended to carry your electrical load for any lenght of time. Only as long as it takes to get set up and start the genset. Reading between the lines it sounds like you would like to avoid running the genset to preserve peace and quiet and reduce fuel use. Virtually any kind of battery you could reasonably expect to use will have risks; mostly from hydrogen production during charging but also from other technical issues. Just look up lithium battery charging issues at Battery University to read all about it. Chances are if the existing battery compartment is a tight fit none of the available options with greater capacity will fit. Your choices are either reduce your power needs so the Group 24 does work or build another larger compartment elsewhere. Neither choice is a trivial exercise. Good luck!

Thanks Elnav. Your response and several others have given me a lot to think about. As you say the RV people are probably not the best to look to for a solution, but I am close to making a final decision. I probably would have headed on into a potentially dangerous situation if the manufacturer had not put the sealed, ventilated, battery box in. That made me think about the danger. Obviously the local dealer had no clue as the cover was off and the vent hose just laying there. I need an evening when it it is not raining with my tape measure to help me make up my mind.

First option is to move the existing battery box to an unused area close by. This will free up room for 3 group 31 deep cycle batteries. My experience in the past with other RVs is that this will be enough reserve. The batts I looked at have an attachment for a vent hose that I can run to the outside. There are also a number of good natural vent options for the area. If I take this route I will drill several holes high on the side of the compartment and put a hat channel over them to the top of the coach. That will be about a 6 foot (2 meter) rise. Since there are openings in the bottom of the compartment, I think this will give a good chimney effect. There is a seperation between the existing battery compartment and the gen set, but I don't trust it enough to ignore the potential.

The second I want to explore is to leave the existing bat as is for gen set starting and add a rack under the coach for the coach bats. Actually I wrote these in reverse order, this is the direction I am leaning.

Right now the coach and gen start are all on the one group 24. I want them separated so I can start the gen set when the coach bats get low without having to turn the truck around and jump it. As is, charging is accomplished by a "Power Center" that recieves 120 V AC from shore power and 12 V DC from the batts and charges when on shore power. The power center also distributes both the 120 and the 12 volt.

Again, thanks for yours and the other good suggestions. -- JHF

Circuit Breaker

I have spent the past 15 years designing and building RV and boat systems. I even worked for Xantrex for a while. If you wish you could send me a PM off line. I might be able to help you in more detail.

I am somewhat concerned by your descreiption of how you plan to drill vent holes.

Regards

You might want to think about using a 12V battery from a Cessna 172. Aircraft batteries can be turned upside down as in aerobatics.

AGM (absorbed glass mat) Batteries. Like the gel cell do not off gas as much. Are vent regulated. With a gel cell will need to change chargers. AGM you maybe able to use the same charger. You will need to check that out.

Circuit breaker there are several issues involved in your query. First of all is increased capacity. Second is out gassing. Lastly but not mentioned is heat accumulation.

If you need more capacity do you know how much? Secondly would a new compartment be better? Is it possible to expand existing location or would a different location be more suitable? What exactly are you using to charge existing battery with .

An unrelated issue is GEL versus AGM Both are sealed so as to be spill proof but both require different chargers and both are easily damaged in the event of incorrect charging. Larger batteries imply needing more charge current. The worst situation is putting in larger batteries but keeping the old charger which then has to run longer to recharge. Unfortunately this also means it keeps the battery exposed fore a longer time in the out gassing zone and this produces more quantities of gas both hydrogen and oxygen. It may also result in greater internal heating. More heat will shorten service life and may increased the potential for other problems.

If your budget allows it the Lithium option is certainly good but expensive.

If you decide to stick with flooded lead acid consider installing hydrocaps which stops outgassing and enhances electrolyte recovery. Going with either GEL or AGM will require changing charger type to a compatible model with lower float voltage levels or you will simply exchange one set of problems for another.

Lots of good advice here, you must decide on what to do exactly.

If it was me, I would measure carefully the available battery storage area and buy the same type (chemistry) of battery as before (charger compatible), but in a size that uses the space better.

I personally prefer the largest "single" battery possible (assuming 12 volt system) as I am a little averse to parallel batteries, but for no real reason.... As long as they are identical in type, manufacturer, age and size it should not be a problem...

Charging slower is also very healthy for the battery......so the old charger usually can be retained.....

Add a fan (explosion proof type) that blows the air away from any ignition sources, possibly in a bit of air trunking to a place above the RV where it can do no harm. The fan can be quite small, you only want a small movement of air, not a blast......especially if the battery box is largely sealed (but not completely sealed, that would destroy the effect needed!), make do sure that a small "draft" actually takes place.

If the Bat compartment is relatively well sealed, add the trunking as mentioned, but add a small fan to blow into the battery box from below, even a brush less PC fan would be acceptable in such a case as long as you get the air direction right first time..... They are usually 12 volts & could be linked so that it only runs while charging......

Do remember that gassing happens mostly while charging and then only once about 13.5 volts is exceeded (depending upon manufacturer etc.).....setting a charger to a max of 13.5 volts would mean that the battery would not ever be fully charged (around 76-85%), but gassing would almost never happen.....

Best of luck in your choice.

Ventilation. How you achieve that is moot and subject to your layout, currently sight unseen.

Hi Wal. Venting was my first thought, but I thought that if not too complicated and expensive a different type of battery may be a good option.

As for venting, I was not sure how much is enough. I would rater NOT use the Myth Busters Method ( The More Bang is Better ) right under my bed! -- JHF