Sealed lead acid battery box drain/vent sizing?

[Deezl Smoke]

 4 sealed lead acid group 31 batteries stored inside a metal truck box. The box is large, at 30" tall, so plenty breathing room. I read that the dangerous gas from a lead acid, sealed or not, is heavier than air and will settle at the bottom of any containment, correct? There may be some hydrogen gas that will go upward.but it can escape through much smaller holes if I read some of the info correctly.

 Looking at the vehicle starting battery box which houses also 4 group 31 lead acids, it is from the factory very poorly ventilated. Just the gaps around the battery cables and a few small drain holes. Very little head room.

 So my question to the membership is, about how many and what size drain holes in the bottom of this box would you think be adequate?

[Kirk W]

Lead acid batteries vent little or no gas while discharging, but explosive mixtures of hydrogen and oxygen can be produced during charging, particularly VLA batteries. Hydrogen gas is colorless, odorless, lighter than air, and highly flammable; oxygen is an oxidizer that can promote a fire or explosion. As long as there is free air movement the veht does not need to be large.  

[Deezl Smoke]

 Thanks Kirk. I'll make certain there is a way at the top to allow gas out.

[Ray,IN]

Deexl Smoke, FWIW the battery compartment in my MH is sealed, sides and top, only the bottom has openings. Even the cables from the house battery bank to the inverter run through an opening near the bottom of the compartment to the inverter mounted in the compartment above the batteries.

I doubt Winnebago would build battery compartments that way if it was unsafe.

1.  

[Deezl Smoke]

6 hours ago, Ray,IN said:

Deexl Smoke, FWIW the battery compartment in my MH is sealed, sides and top, only the bottom has openings. Even the cables from the house battery bank to the inverter run through an opening near the bottom of the compartment to the inverter mounted in the compartment above the batteries.

I doubt Winnebago would build battery compartments that way if it was unsafe.

1.  

 Thank you Ray. In discussion locally, that very scenario comes up a lot. So long as the compartment can not "pressurize", most seem to think all should be good.

 I am thinking the drain holes in the bottom, and a small bulkhead in the top with something like a gear box vent to keep water out when I wash it, should be sufficient. ?

[Jaydrvr]

Your title says you're using sealed lead acid (SLA) batteries, which suggests they're AGM batteries. These typically have an emergency valve, but are otherwise fully sealed. SLA batteries do not outgas under normal charge/discharge cycles, only under extreme or unusual conditions. Only if they're conventional lead acid batteries do they need venting. Jay

[Kirk W]

47 minutes ago, Jaydrvr said:

Only if they're conventional lead acid batteries do they need venting.

The following comes from Interstate Battery sourced article. It is rather like using a seatbelt. You really don't need one at all, if nothing ever goes wrong.

AGM batteries are a type of lead-acid battery that contain a glass mat that absorbs hydrogen gas as it's produced. However, if the battery is overcharged, charged too quickly, or doesn't have enough ventilation, hydrogen gas can build up and become dangerous. This gas can contaminate breathing air or cause an explosion if it reaches the right concentration. To prevent this, AGM batteries should not be operated in a sealed container and the relieved gas should be allowed to dissipate into open air. 

Edited Tuesday at 01:16 PM by Kirk W
Add information.

[Jaydrvr]

For years many AGM manufacturers were advertising freedom in placement for their batteries, but in looking at the Lifeline and Fullriver websites it looks like they've changed their tune. I'm guessing the lawyers contacted the marketing departments. Jay

[Chalkie]

2 hours ago, Jaydrvr said:

For years many AGM manufacturers were advertising freedom in placement for their batteries, but in looking at the Lifeline and Fullriver websites it looks like they've changed their tune. I'm guessing the lawyers contacted the marketing departments. Jay

You may not be able to place them in some of the directions that used to be advertised, however, the AGMs really can take a beating. I used them for years in ATVs and my off-road truck. Nice not to worry about acid spills brought on with the bouncing around.

[Deezl Smoke]

 My luck is such that I would be "that" one anomaly that gets a leaker. I don't want to get too many or too big of holes in the box, but I do plan to have some way for it to breath a bit.

 Thank you for the replies.

[Steven@146]

We too were looking at having to replace our single group 27 lead acid battery after 5 years. We are in a little different situation with a 5th wheel. I was looking at replacing our battery with an AGM so I would not have to keep checking the water/acid level in our OEM battery. The OEM battery box has a 2 inch hose from an outside intake going in the top of the battery box, and a 2 inch hose leading out the bottom of the battery box to the underside of the RV.

Then I got to looking at the cost of an AGM battery and found that the cost to upgrade to a good LifePo4 battery was less or the same as an AGM. Also I got to looking at the efficiency of a  Lithium ion phosphate battery over an AGM considering deep discharging and number of times of discharging and possible longevity. Why not just go to a Lithium and no venting required.

But now switching to a Lithium battery brings in a whole lot of other considerations, namely the amperage a Lithium battery can take to recharge, what type of converter/charger do we have? Is C/C Lithium capable and what wire sizes and lengths that is already installed in the RV. Not to forget how we want to use our RV and camp and how much boondocking we want to do.

We have no solar and do not have an inverter but do have a 30amp genny. Also we  have to keep in mind we intend to convert our absorption refrigerator to a JC Refrigeration 12VDC dual compressor which will place an additional burden on the 12VDC system. A lot of things for us to think about and research before switching over to Lithium.

After doing some research and keeping it simple/cost effective, we did switch to a LifePo4 100ah battery with a good reputation/recommendation for the cost of $185. It has low temp cutoff and bluetooth so I can monitor the "goes into" and "goes out "of voltage and amps/hours. Also we did not have to rewire the RV or replace any of the 6 gage wire in the RV.

The WFCO converter/charger we have is an auto detect Leadacid, AGM, Lithium unit but they don't have a stellar reputation. So I installed a 20amp external LifePo4 only smart charger ($90) connected directly to the Lithium battery in the front cargo hold. We don't have to rely sole on the WFCO converter/charger to charge the LifePo4 battery. Now a 20 amp external LifePo4 charger isn't going to win any races (@ 15-18 amps going in) charging a Lithium battery but the way we camp and travel, we are not in a hurry, I think it will be ok. It's only turned on to charge the Lithium battery, then turned off. The WFCO converter/charger supplies the 12VDC to the house.

We only travel @ 5 hours a day before camping and hooking to an AC power grid. The Lithium battery should hold the 12VDC fridge that long before we get plugged back in to the AC grid. Given also that the fridge once cold will not run the compressors all the time. We always have the genny if we boondock overnight, if rarely we do.

Testing I completed charging the Lithium battery used down to 70% SOC, the WFCO would charge the battery up to 100% but it took 7 hours to do it not in Lithium mode. You can't rely on the WFCO to stay in Lithium mode. You can not hard set it to Lithium mode easily. The same test with our new external Lithium 20 amp smart charger did the charge up to 105% in less than 2 hours.

I do have an isolation switch that I can isolate the Lithium battery from the WFCO converter/charger, so the external Lithium charger is not competing with the WFCO.  Once the Lithium charger has recharged the battery, it's turned off, and the battery through the switch is reconnected to the WFCO converter, the WFCO will then maintain the battery at 105%.

Another thing to consider is how our 1 ton tow vehicle with it's 220 amp alternator smart charging system will respond having a lithium battery installed in the RV. Time will tell, but It probably will charge the RV Lithium battery very little if at all only putting out @ 5 amps or less.  Again the 12VDC fridge will not be running all the time but a maybe lot of the time, but the Lithium battery should hold the fridge until we get to our next campsite and plugged back in to an AC grid. If it becomes an issue I'll think about installing a DC to DC charger.

Now for a backup to our genny backup, I was looking into a Renogy suitcase 100 W 20amp, Lithium capable controller solar panel kit for $200. Probably will put out less than 10 amps if we decide to get one. Reviews report @ 7-8 amps. I can still isolate the Lithium battery from the WFCO. Charge the Lithium only with the solar panel OR the external Lithium only 20 amp charger but not at the same time.

Converting to a LifePo4 battery brings in a lot of other considerations but in the long run it maybe worth the cost for some RV owners.

Edited 22 minutes ago by Steven@146

[Deezl Smoke]

 I fully agree on the lithium iron. Those things are awesome. I have been watching and learning a lot about the charging and other consideration when switching to lithium ion or iron. Of course I would go iron as the thermal runaway is far less likely. But I already have the sealed lead acids, though they are aging. But for my usage, at least until these batteries start to fail, the sealed lead acids will do fine.

 I'm still a weekend warrior camper. My needs for this set of batteries is not very heavy. Mainly for when I'm.......(I don't like calling it stealth camping) what I might call nomading it? I will end up for the night in a somewhat noise sensitive area and not wish to run the generator, though it is a quiet one, to make my coffee etc in the morning, or popcorn in the evening. Otherwise they  just power a few led lights.

[Steven@146]

2 hours ago, Deezl Smoke said:

 I fully agree on the lithium iron. Those things are awesome. I have been watching and learning a lot about the charging and other consideration when switching to lithium ion or iron. Of course I would go iron as the thermal runaway is far less likely. But I already have the sealed lead acids, though they are aging. But for my usage, at least until these batteries start to fail, the sealed lead acids will do fine.

 I'm still a weekend warrior camper. My needs for this set of batteries is not very heavy. Mainly for when I'm.......(I don't like calling it stealth camping) what I might call nomading it? I will end up for the night in a somewhat noise sensitive area and not wish to run the generator, though it is a quiet one, to make my coffee etc in the morning, or popcorn in the evening. Otherwise they  just power a few led lights.

Yeah I screwed up and used "ion" and "Iron" interchangeable. not the same I fixed it. The BMS in the Lithium battery protects the battery from runaway. I understand on running the genny. There are some camps that don't allow running a genny or only at certain hours. And some don't like generators and the emissions they put out. The newer external inverter gennys are very quiet but some motorhome gennys can be a little louder. That's why we are looking into at least a minimal suitcase solar panel if we can't run our genny or can't get gas to run it. Unfortunately our genny is not dual fuel, gas only, so in a prolonged power grid outage a solar panel would come in handy.

 

Edited 1 minute ago by Steven@146