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Old 08-01-2008, 15:29   #1
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Should My Batteries Be Gassing??

I have a set of 4 Trojan T-105's. They have a set of Iota DLS-90's working as the charging system. I also have a Link 10 Battery Monitor.

Right now, I am connected to shore power and have been for approx 30 hours straight. One of the chargers is plugged into shore power to keep the batteries topped off.

Prior to this shore power connection I had been draining the batteries to 50% of capacity and then charging them up to 90% of capacity, using a genset.

Now, after 30 hours of charging, I'm *still* getting gassing! The Link 10 says I'm putting 1.5 amps (12V DC) into the batteries. The Iota chargers is showing a solid light indicating a "float charging" state.

Why am I still getting hydrogen gassing?? Is this normal? Is the DLS-90 supplying too much float charge?

I am concerned because it disrupts my ability to detect CO. CO detectors are (conveniently for boaters and such) set off by hydrogen gas as well.

Any idea if I should still be seeing the release of hydrogen after 30 hours of charging and 1.5 amps of charging current?

Thanks
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Old 08-01-2008, 15:43   #2
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Gassing

Sean,
Flooded lead-acid batteries will gas at float voltage and above. The question is how much gassing is being observed. Imagine a curve demonstrating liters per hour of gassing versus applied voltage to a fully recovered and charged flooded battery. There is a very soft "knee" to the curve. The amount of gassing when full at an applied float voltage does not cause significant loss of water in one to three months yet may still require some water addition in 6 months.

Naturally recommended float voltage is inversely proportional to temperature yet some variation is tolerable. My guess is that in your situation the batteries are almost always wanting to charge accept current because they have not been allowed to fully recover with limited charging times available and, therefore, they will gas much more at float voltage than they would if truly recovered and full yet not as much as when at the end of an acceptance cycle before going to float.
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Old 08-01-2008, 16:08   #3
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Just for grins, what does your hydrometer say? Are all cells equal?
What is your float voltage really? Have you measured it?
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Old 08-01-2008, 17:40   #4
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Thanks, Rick. That makes perfect sense. So if the batts are gassing a bit more due to the fact that they have never (in their few month life) been up to full charge, do you think the gassing will reduce to "normal" levels after they stay in a fully charged state for some time?

Data: My CO detector puts my H2 levels at 30PPM at waist level. Since H2 is lighter than air, I am assuming it is a good deal higher than that up by the roof. Based on the MSDS for H2, 4% in air is the lower explosive level, requiring a level of 40,000PPM in order for me to get in a dangerous situation. I think I'm well below this.

Also, for senior mechanico - I'll admit I'm not using a hydrometer. However, the float voltage is at 13.6VDC. Sound right?




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Sean,
Flooded lead-acid batteries will gas at float voltage and above. The question is how much gassing is being observed. Imagine a curve demonstrating liters per hour of gassing versus applied voltage to a fully recovered and charged flooded battery. There is a very soft "knee" to the curve. The amount of gassing when full at an applied float voltage does not cause significant loss of water in one to three months yet may still require some water addition in 6 months.

Naturally recommended float voltage is inversely proportional to temperature yet some variation is tolerable. My guess is that in your situation the batteries are almost always wanting to charge accept current because they have not been allowed to fully recover with limited charging times available and, therefore, they will gas much more at float voltage than they would if truly recovered and full yet not as much as when at the end of an acceptance cycle before going to float.
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Old 08-01-2008, 17:54   #5
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So how much water are you adding for the whole bank and how often? Do they go down evenly?
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Old 08-01-2008, 17:57   #6
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13.6VDC for T-105s is about right.

The Iota's...assuming you have the smart-charging IQ-4 option...will automatically go into an equalization cycle after awhile. When this happens, you'll see voltages above 14 for a time, then they'll drop back to float levels. I've forgotten the interval for this...it may be every week or two.

I don't see much gassing in the T-105's on my boat (8 of them) or in my ham shack (four of them) or my workshop (two of them) when at the float levels of 13.2 to 13.6VDC.

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Old 08-01-2008, 18:08   #7
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So how much water are you adding for the whole bank and how often? Do they go down evenly?
Paul, the batteries are a few months old. I've never had to add any water at all. It's more the H2 coming off that I'm concerned about, since it's disrupting my abillity to detect carbon monoxide.

I have the same setup I had on the boat I sold. When I was at the dock with that boat, I have to assume the batteries may have gassed as much, but the air flow kept the H2 from hitting my old CO detector. This time, the air flow blows the H2 right past the CO detector, giving me false readings.
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Old 08-01-2008, 18:10   #8
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13.6VDC for T-105s is about right.

The Iota's...assuming you have the smart-charging IQ-4 option...will automatically go into an equalization cycle after awhile. When this happens, you'll see voltages above 14 for a time, then they'll drop back to float levels. I've forgotten the interval for this...it may be every week or two.

I don't see much gassing in the T-105's on my boat (8 of them) or in my ham shack (four of them) or my workshop (two of them) when at the float levels of 13.2 to 13.6VDC.

Bill
Thanks for the sanity check, Bill. I do have the IQ4 option. I see a bubble of H2 every second or so in any given cell (sometimes a few bubbles pop up at the same time). Is that the kind of gassing you are seeing?
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Old 08-01-2008, 18:21   #9
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I would think if you are not losing water the gas isn't that much. You would lose water if it was gassing a lot. My float measure a bit different as i don't leave the boat plugged into the charger. The solar panels do it well enough that I don't need to be plugged in all the time.
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Old 08-01-2008, 19:25   #10
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Yep, that's it. By the way, my Iota and Victron chargers are on all the time when at dockside. And, at home, the Iota charger is on continuously.

About a year ago I added WaterMiser caps. They seem to help in prolonging the period between needing to add a bit of water. And, they make checking the water levels very easy and quick, with their flip-up tops.

However, you've still gotta check the water levels frequently. Occasionally, you'll find, it IS necessary to add some. Thus far, I've not been able to correlate this with variations in temperature, humidity, etc. It almost seems that every once in a while the batteries just decide to give up some water....just to keep you on your toes :-)

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Old 08-01-2008, 20:04   #11
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Vigorous gassing

Sean,
Your description of gassing is of something waaaay below what is called vigorous gassing. If you have a stethescope applied to a side of one battery you can hear the difference in the rate of bubble formation as float voltage might be varied from 13.2V to 13.5V @20deg C for a full battery and be surprised at the differences. Regardless, this would be normal float gassing.

Vigorous gassing is when you can see constant bubbling at the surface of the electrolyte with attendant droplets that rise above the surface and fall back in. Above that level large "burbing" bubbles also form which would indicate a dangerous level of gassing for any extended period.

BTW: The gas contains a mixture of O2 and H2 with twice the number of H2 molecules as O2 molecules on a molar basis. It takes a complicated means of separating the hydrogen from the oxygen in open air. I believe that your CO detector is detecting a lower content of Nitrogen compared to other smaller molecules.
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Old 09-01-2008, 00:51   #12
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Firstly, 30PPM of hydrogen is nothing to be concernd about. But that must be some sensitive meter.
My main question is, why do you have the batteries venting to the inside of your motorhome?? If you do happen to get a gassing issue at sometime, it is not the hydrogen that is of concern.The fumes that can be emitted if a boil up of the battery occurs, stinks and can cause some nasty damage. The batteries should be vented to outside for saftey sake.
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Old 09-01-2008, 07:45   #13
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Firstly, 30PPM of hydrogen is nothing to be concernd about. But that must be some sensitive meter.
My main question is, why do you have the batteries venting to the inside of your motorhome??

The short answer is laziness. ha ha

I haven't finished my combination battery enclosure / bench seat yet. This enclosure was to have provided a space for the batteries with their own environment away from the main living area. For now... the batteries are exposed to the main living area air.

Venting batteries is always a difficult issue. On my boat, there was literalliy no way to do it aside from venting them into the salon and then up through the main living air and out the companionway hatch.

Same story in this motorhome. The batteries rest of the floor of the motorhome and are up forward by the driving area. Since H2 is lighter than air, if I want to vent by natural means (no fan), I would have to run a pipe up through the entire place to the roof and let that draw the H2 out at the roof level. Not a great option, as much like the deck of a boat, the less holes the better.

The only other way to vent would be to drill holes in the floor and try and force the H2 *down* with a fan.
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Old 09-01-2008, 09:07   #14
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"I would have to run a pipe up through the entire place to the roof and let that draw the H2 out at the roof level."
Not really. A casual "fume hood" over the batteries, even some plastic sheeting that lead up into a funnel and from there to some inexpensive vinyl tubing, should do. Since the hydrogen and warm gasses want to go UP, and there's not a lot of volume or pressure involved, a run of thin cheap vinyl tubing should be all you need to lead it "up" and then out wherever a 1/2" tube can be snuck. (And I'd suspect even a 1/4" tube would suffice.)
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Old 09-01-2008, 09:13   #15
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"I would have to run a pipe up through the entire place to the roof and let that draw the H2 out at the roof level."
Not really. A casual "fume hood" over the batteries, even some plastic sheeting that lead up into a funnel and from there to some inexpensive vinyl tubing, should do. Since the hydrogen and warm gasses want to go UP, and there's not a lot of volume or pressure involved, a run of thin cheap vinyl tubing should be all you need to lead it "up" and then out wherever a 1/2" tube can be snuck. (And I'd suspect even a 1/4" tube would suffice.)


Hmmmm.... flexible vinyl tubing is a good idea. I hadn't thought about a flexible tube.

I wonder... do you need to set up the tube like a mini chimney? I know a chimney really can't run horizontal (or close to it) for any stretch of the run or it will fail to draw.

The way things are set up, the batteries are on the "port" side of the RV and I have a complicated refer venting system on the "starboard" side of the RV. I could pipe the battery gasses to the top of the refer venting system, which has a nice draw to it all the time. Only thing is... does the H2 keep pushing through a twisty mess of vinyl tubing. Any thoughts?

Or... if I seal the battery compartment off air tight, maybe the slight pressures involved when the gas is generated would help push it along a less than perfect vinyl tube route?
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