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Old 11-17-2020, 11:22 PM   #1
whutfles
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AGM Batteries - Venting and Disconnect Switch

I am on my 2nd set of AGM batteries and like them. I got to wondering if they needed to be vented? So I googled "Do AGM batteries need to be vented"? I found an article by RV Nerds titled "Electrical Myths, Part 4 AGM Batteries Don't Need Venting" By Dave Nov 1, 2017.

The article explained how they do need to be vented because they can release hydrogen gas in an overcharge situation. Then they quoted numerous organizations and their rules on ventning. One was this:

RVIA
The Recreational Vehicle Industry Association’s Low-Voltage similarly requires venting for all battery locations, whether or not batteries are actually installed, and prohibits installation of other potentially spark-producing equipment in the same compartment (e.g. inverters, charge controllers, disconnect switches):

Now I have read on this Forum many accounts of owners suggesting installing a battery disconnect switch to avoid the arcing when disconnecting a terminal and to avoid the drain when in storage. So I installed a disconnect switch and yes it is in the same compartment as the battery. Is that paragraph above from the RVIA correct and still in effect? And what is the difference in having a disconnect switch in the same compartment or not having one and getting the almost always spark when you connect or reconnect the battery terminal?
 
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Old 11-18-2020, 09:06 AM   #2
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Since I'm not building my units to sell I guess I don't worry about what RVIA has to say. I do vent both my AGM batteries, but over the different rigs I've had charge controllers, inverters and battery disconnects have all been located up there somewhere. They all had some type of battery disconnect.
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Old 11-18-2020, 02:32 PM   #3
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Most quality battery switches are non-arcing switches meant for use in the same compartment as lead acid batteries which do vent a lot of gas on occasion. Agm batteries were developed for use by the military in sensitive locations and can be mounted in any orientation. It would be a very rare circumstance for them to vent at all. I use two group 31 agm batteries mounted in battery trays bolted through the compartment floor and connections are covered and protected, but not vented. The factory cables have been replaced with marine grade two gauge cable using sealed marine grade tinned copper sealed lugs secured with a five ton hex crimper tool. The factory cable connections using cheap thin hand crimped automotive connectors were not to my standards.
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Old 11-19-2020, 06:20 AM   #4
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How does a gel cell work?
A gel cell is a "recombinant" battery. This means that the oxygen that is normally produced on the positive plate in all lead-acid battery recombines with the hydrogen given off by the negative plate. The "recombination" of hydrogen and oxygen produces water (H2O), which replaces the moisture in the battery. Therefore, the battery is maintenance-free, as it never needs watering.

The oxygen is trapped in the cell by special pressurized sealing vents. It travels to the negative plate through tiny fissures or cracks in the gelled electrolyte.

The sealing vent is critical to the performance of the gel cell. The cell must maintain a positive internal pressure. Otherwise the recombination of the gasses will not take place, and the cell will dry out and not perform.

In addition, the valve must safely release any excess pressure that may be produced during overcharging. Otherwise, the cell would be irreparably damaged.

It's important to note that gel cell must never be opened. If opened, the cell loses its pressure, and the outside air will "poison" the plates and cause an imbalance that destroys the recombination chemistry.
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Old 11-19-2020, 08:47 AM   #5
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I'm still a lead acid wet cell user. We dry camp as much or more than with hook-ups. I've installed disconnects, inverters, auxiliary chargers, battery monitors, transfer switches, etc... in the same compartments in every unit we've owned. In fact, some units came from factory with simply an open battery compartment to the entire basement area. I make sure our battery bank is vented top and bottom to the outside and never give it another thought.

I'll skip over AGM technology as I've never had the need, and go straight to Lithium's next time. Probably be about 6 years as I just loaded our Montana with 470AH of 6 Volters this spring.
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Old 11-20-2020, 04:08 PM   #6
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AGMs have virtually no gassing under normal operating conditions: Unlike flooded cells, gel cells and AGMs are hermetically sealed and operate under pressure to recombine the oxygen and hydrogen produced during the charge process back into water.
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Old 11-20-2020, 04:32 PM   #7
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We have had 4 battery's for 5 years now (2-6 volt and 2 12-volt wire together) with no venting what so ever and have never had any issues. The compartments in most if not all campers are FAR from air tight and are self venting IMHO
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Old 11-20-2020, 07:43 PM   #8
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I am with DQDick that it doesn't matter what RIVA says they only suggest code for the industry and are not an enforcement agency. We own our coaches and can do what we want within limits.


Likewise I will agree that our battery compartments are not airtight to begin with and as such should have more than enough venting.


Finally if you are opening up a compartment to flip a switch, I expect that will vent any gas buildup to the point it is below explosive limit real quick. I wouldn't put an open flame directly in the compartment trying to make the gas explode but really can't see the concern under normal operations.
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Old 11-21-2020, 05:35 AM   #9
Jeff n Susan
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how are the AGM batteries with freezing? Can they take it? or do they have to be tickled all winter?
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Old 11-21-2020, 06:23 AM   #10
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Glad I switched to lithium. No worries about hydrogen venting.
Just have to think about lithium batteries catching fire and exploding...
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Old 11-21-2020, 06:27 AM   #11
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Originally Posted by Daryles View Post
Glad I switched to lithium. No worries about hydrogen venting.
Just have to think about lithium batteries catching fire and exploding...
Isn't that like going from the fuel to the fire.. I think I'll stick with the old school flooded batteries. Lol
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Old 11-21-2020, 06:30 AM   #12
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how are the AGM batteries with freezing? Can they take it? or do they have to be tickled all winter?
Wives should be tickled not batteries

Looking at the chart here they show data down to -20 I doubt I will see -20 in central Texas
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Old 11-21-2020, 07:15 AM   #13
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Trickle or Tickle? Too much of either can lead to expelling gas.
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Old 11-25-2020, 02:25 PM   #14
bcrvman
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Quote:
Originally Posted by whutfles View Post
I am on my 2nd set of AGM batteries and like them. I got to wondering if they needed to be vented? So I googled "Do AGM batteries need to be vented"? I found an article by RV Nerds titled "Electrical Myths, Part 4 AGM Batteries Don't Need Venting" By Dave Nov 1, 2017.

The article explained how they do need to be vented because they can release hydrogen gas in an overcharge situation. Then they quoted numerous organizations and their rules on ventning. One was this:

RVIA
The Recreational Vehicle Industry Association’s Low-Voltage similarly requires venting for all battery locations, whether or not batteries are actually installed, and prohibits installation of other potentially spark-producing equipment in the same compartment (e.g. inverters, charge controllers, disconnect switches):

Now I have read on this Forum many accounts of owners suggesting installing a battery disconnect switch to avoid the arcing when disconnecting a terminal and to avoid the drain when in storage. So I installed a disconnect switch and yes it is in the same compartment as the battery. Is that paragraph above from the RVIA correct and still in effect? And what is the difference in having a disconnect switch in the same compartment or not having one and getting the almost always spark when you connect or reconnect the battery terminal?
Well that's just both hilarious and sad. My old flooded lead acid batteries were within inches of several large breakers for the house circuit and the hydraulics plus all the electrical stuff to operate the hydraulics. Yes the battery box was vented through the floor and to the outside front, but there was still a non zero probability explosive gas could escape. I have since replaced with Lithiuim so don't care but others might want to check closely.
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Old 11-25-2020, 02:26 PM   #15
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Isn't that like going from the fuel to the fire.. I think I'll stick with the old school flooded batteries. Lol
Those are a different kind of Lithium battery.
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Old 11-25-2020, 02:29 PM   #16
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Originally Posted by Daryles View Post
Glad I switched to lithium. No worries about hydrogen venting.
Just have to think about lithium batteries catching fire and exploding...
The Lithium batteries you have heard about catching fire are either Tesla or laptop/phone. They are different chemistry than the LiFePO4 in your RV. Even flooded lead acid have caught fire when overcharged to the point of boiling off all the water.
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Old 11-25-2020, 03:15 PM   #17
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Originally Posted by jeffba View Post
Wives should be tickled not batteries

Looking at the chart here they show data down to -20 I doubt I will see -20 in central Texas
Cold is not the issue with AGM, however heat is AGM batteries do not do well in very warm climates, you being in Texas you should consider reverting to wet cell.

Personally Wet is the way to go, venting is very easy and you can also add a automated watering system very easily. And AGM does not have near the life of a maintained flooded battery.

Lithium while a good solution they should be cooled in hot climates but the bigger issue is unless you plan to keep your RV for 15-20 years the cost is a loser. Owning a Tesla's for 6 years (on 3rd one) I have great appreciation for Lithium batteries but I also appreciate the safegards built into the Tesla to protect the batteries and their thermal management (both under load and while charging)
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Old 11-29-2020, 09:46 PM   #18
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Sticking to my wet cell

My 2012 Monty has the original wet cell. Plan on replacing with another wet cell this spring just due to age. My unit stays plugged in all the time it’s not on the road.
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