Sure I like the idea of adequate venting explosive gasses and am considering ways to improve my own situation. That being said, Id venture a "pure guess and speculate" using a cooler as a battery box may yield some temperature issues. That takes some work and dusting off the old thermodynamics books YUKKKKKKKK lol To give an accurate engineering answer I would have to know the volume, and R value, and ambient temperature,and air flow around the cooler,and venting CFM, and then the watts, in order to calculate the temperature rise or temperature inside the box during charging. With respect to using a cooler (an insulated fairly tight enclosure) as a battery box it boggles my mind to try to pin a specific temp range, but there are smarter folk than I around here. It seems like you would have to consider rate/duration of charge, artificial ambient temperature, internal heat generation, rate of temperature increase, rate of heat disipation. I believe catostrophic failure for most of lifelines AGM's occur around 320 degrees, but I have no idea of a specific temperature that would indicate onset of a thermal runaway. I could be wrong, but I don't know if it's so much a matter of a set temperature that thermal runaway can occur so much as the rate of thermal increase. Others may have more ideas, but to me, the best defense against that is using a temperature compensated charger to begin with, provide adequate air flow, and don't store/charge your batteries in direct sunlight. While it is true that AGM's are more suseptable to thermal runaway, it takes a pretty extreme set of circumstances to occur. It actually wouldn't be desireable to have an air tight battery box as your batteries need to be able to dissipate heat generated during a charge cycle. Jerry, isn't your battery compartment already enclosed? Is there a specific reason you want them boxed? Typically, those cable exits are fairly well covered to direct elements and not necessary to completely seal them. PS I like that marine device, sounds much safer !!!!!!!!!!!!!!!!!! no reason I couldn't use something like that I'm glad to hear how convection alone can vent the gas, wheYou REPORT, now its up to me to DECIDE. If a small 12 VDC Muffin Fan were installed, I think it would be safer to mount it OUTSIDE THE BOX with its bladé and shield assembly up against and blowing air INTO the box to create a positive pressure forcing any possible combustible gasses out the safe vent holes rather then pulling them past the electric fan. Inverters can also have a vent fan that cycles upon temperature and there is yet another potential spark producing device which maybe isn't a good thing to have near the batteries? Very interesting and safety related post, thanks I THINK I LIKE THE FIRST METHOD (blow air in creating a positive pressure so air and gas vents out the holes versus the fan) The alternative would be pulling air INTO the box (via its vent holes) then venting that air plus any gasses out via the fan. INSTALLATION CONCERNS: I guess? I will mount it (can yield sparks ya know) outside the box up against it to blow air INTO the box creating a slight POSITIVE PRESURE so any gasses get pushed out the boxes existing vent holes. Although I was already aware of this issue and am normally very safety minded, this post got me thinking so I am going to get that small fan installed, its a cheap and easy fix which I will install on the opposite and lower side from where the batteries are. On mine I'm thinking about adding a small 12 VDC muffin vent fan to create forced air ventilation out the box because my relatively small RV (29ft Class C) lacks room for all my accessories. The obvious hazard is if the batteries are outgassing explosive vapors which get trapped and aren't vented to the exterior and can accumulate, then say the fan on the Inverter kicks in that can create a spark YIKES. (I think the gas is slightly lighter then air right?). HOWEVER (must confess) mine are currently but the compartment is well vented above the batteries and to one side as well as the bottom, plus the Inverter is on the floor at a lower level. If I had my "druthers" I would NOT have an Inverter (a device that creates a spark) in the same air space as flooded lead acid batteries.
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