building a vented battery box

[GotSmart]

I had a custom steel 1/8 inch box made io insert into the floor.  1 inch clearance around the sides of the batteries.  They are sitting on furring strips to give a little more ventilation. I lined it with an old tractor tire tube that I cut up.  I drilled 1/2 inch holes in a few places both high and low for venting.  The lid of the box also has rubber mounted on it. 

I have 4 AGM sealed GC units in it.  No problems.

 

[Vanada]

I've been looking at every thread about battery boxes I can find here and this one is the most comprehensive so far... I'ma hijack it.

Having flip-flopped back and forth between options I'm getting to my wit's end and am considering just getting one of these:
http://www.allbatterysalesandservice.com/browse.cfm/4,9098.html

My confusion though is in that these aren't totally sealed. They have openings for cables to pass in and out but those are pointed downwards, I assume by design. Would it still be safe to use one of these inside the van and vent it to the exterior via a hose out the top?

Cheers,
Tom

 

[ccbreder]

That is a good price.

 

[SternWake]

These boxes are battery containers, allowing multiple battery cables/wires to easily enter and exit.

Meaning it is not a sealed vented battery box, it is a vented battery container that will passively vent battery gasses to the immediate environment when absorption charging.

Those wishing not to have battery Absorption gasses enter van living area need more strategy other than just this product.

I have an old 12v battery box and it would prove quite difficult to actually seal it and add instake and exhaust ducts. But it worked great at keeping things off the top of the battery, and contain spills.
If flooded batteries, in a vented sealed container were my intention, I might use the lower portion of the battery box, but would redesign the lid so I could seal it tight and force fresh air into it which would exhaust out a tube.

Perhaps build a removeable Lid out of acrylic and superglue

I'd likely use Pass through studs/Feed through connectors for the cables rather than pass cables through the box.

These require more ring terminals and connections and thus add resistance and possible failure points, but can make for a much cleaner install.

https://www.bluesea.com/products/category/27/Feed_Through_Connectors

I would add a small super low CFM computer muffin fan as an intake fan to push Air out a hose. Ideally it would only be activated in the 14.1v range.

This would also be good for batteries in warm environments that get alternator recharged when depleted, as the batteries warm a surprising amount in such conditions.

I use a Sunon 40MM 0.03amp 12v fan inside my 12v compressor fridge, but cannot find the exact product anymore to link.

I really like Noctua fans One of these with the provided low noise adapter cable(simple resistor) would be more than adequate.

https://www.amazon.com/Noctua-Cooli...=1486664710&sr=1-2&keywords=40mm+computer+fan

 

[Vanada]

Thanks again SternWake! That's what I thought... Back to the drawing board it is I guess!

I don't know why I'm shying away from building a box. Confidence maybe... The other thing I was thinking was to find a Coleman or similar cooler which is about the right size and make that work. They're bulkier than I would like by a long shot and I don't know how that plastic would respond to a spill. At least they're insulated which might help slightly with temperature control.

 

[SternWake]

The plastic in coolers would not like it if sulfuric acid dripped down the sides of the battery, which will happen if overfilled when not already fully charged. Also the battery itself would likely be able to crack the plastic on the bottom and the insulating foam within the cooler will dissolve leaving just the plastic shel.l

As far as battery temperature, If one is capable of higher charge rates, one wants their batteries to easily be able to shed heat, and does not want to insulate them. Lifeline says to keep 1/4 inch between batteries and around their sides for ventilation.

In cold temps one can utilize the heat generated during charging to try and keep the batteries warmer overnight and thus allow them to retain more of their capacity in cold ambient temperatures, but this might be a futile endeavor depending on a few factors, like ambient temperatures/ battery location, recharge rate, ect.

There are all sorts of ways to dealing with flooded battery offgassing, from ignoring it completely, to the other end of forced exhaust of a sealed container.

As far as forced air movement, one either pushes air into a sealed container, or one pulls it out. Pushing it is safer as there is no risk of hydrogen or oxygen seeing a spark from the fan, but the box must be pretty well sealed. How much of a risk is pulling it? Hard to say. But when pulling it, there has to be a passive air inlet.

So a vented sealed battery box needs an inlet and and outlet, and of those two I would rather put a small very low cfm low amp draw low noise fan pushing air into an otherwise sealed box, and have a flexible tube to push out the gasses in the direction of choice.

Flooded batteries only offgass when charging*, when the batteries reach ~14.1v or higher. Higher amperage to get the battery to absorption voltages faster will cause more gassing, starting earlier and more volume of gasses.
The goal should be to make sure no gasses can build up, and cannot be smelled/ noticed/ breathed by humans or pets. Regardless of if it has killed or not, is carcinogenic or not, I don't think anybody would argue it is healthy, but one never knows.

* flooded batteries can offgass when discharged at very high rates too, or if a cell shorts out.

If I were to build a box for batteries, I would use 1/2 inch( or thicker) baltic birch plywood, using pocket screws and glue, no frame. I would make sure there was 1/4 inch or slightly more space around each battery.
I would use the Blue seas pass through studs or similar.
I would recess the Noctua 40MM fan into the plywood and use a grille to protect the blades. On the top of the box I would have another 40MM vent with a tube. The top would be a lift out hatch that rested tightly within the sides with some thin weather stripping to seal it.

There would be a method to secure the batteries within the box so they cannot move within it.
The box would have several attachment points so it could be held to vehicle floor/walls, and could not move if the vehicle rolled.

I think far too many people simply rely on gravity and the weight of a battery to keep them in place rather than securing them properly.

This is as unwise as not fusing properly, althought it works 'just fine', until Murphy decides the time has arrived to make the worst of a possible scenario.

Making this box is perhaps not something one has the carpentry skills/tools to achieve.

I would not really have an issue attaching a slightly more powerful 40Mm exhaust fan to the Lid of the passively vented plastic battery box, and have it on continuously expelling charging gasses outside the vehicle when charging. Most computer fans are brushless and make no sparks, and the gas build up would have to be rather concentrated before ignition could occur, which likely could not happen unless one went through efforts to actually make that occur.

 

[SternWake]

I was trying to find a product which could be adapted to forced venting of battery gasses.

Here is something along the lines of what I had in mind, but at a 40MM diameter, not 92MM

All sorts of products can be adapted:
https://www.amazon.com/Diameter-Flexible-Connector-Stretch-Drainer/dp/B01GYWPGBK

The hard part is connecting it to the fan/ Lid

 

[Vanada]

I thought I had recollection of asking about the pass-through studs here and being told it was better to do it inside. Eh, I'll look it up again later. With a sealed box my plan was to use these to allow cables in and out: https://www.homedepot.ca/en/home/p.flexible-cord-connectors--12-in.1000124760.html?autoSuggest=pip

Just did a bit of research on pocket screws / holes. Seem like they might not be too complex. Of the ply boxes I've seen marine folk building most employ epoxy or something on the inside for spills. Canadian Tire do have some basic spill catching trays which I trust are made using the right plastic but I don't know that they're the right size.

Again, more thinking to be done. I like to do things properly but without getting depleted mentally or financially!

Cheers!

 

[SternWake]

Those cord grips are nice, but one needs to basically push the wire through, then attach the ring terminal. The ring terminal diameter is too wide to push through most of those cord grips, and still allow it to grasp the wire tightly.

The pass through studs require one to cut the wire, than add 2 more ring terminals on each part of the cable, which introduces electrical resistance and possible failure points. Which can be negated by fatter copper and top quality crimping/soldering.

Everything is a compromise. many ways to accomplish the same function, but one must put some thought into longvity of that function, as well as overall safety.

Pocket screws make joinery easy, and very solid, even without glue. The glue makes it slightly more difficult is it acts like a lubricant and the work can move while driving the screw. Part of the bonus about pocket screws are one does not require clamps, but if the work moves bacause glue is acting as a lubricant, then the clmaps are required anyway, if one is seeking a high level of precision.
One could drive the screws without glue, then back them out, apply the glue then retighten.

I am not sure of epoxy's resistance to battery acid, or what would be best to line the box with.

I might have to do an experiment the next time I bust out my Hydrometer, as i have plenty of cured epoxy about to put a few drops of sulfuric acid upon.

 

[Vanada]

Here's what I think I'm going to go with:
- Build a box out of 3/4" ply I have sitting around, butt joints and glue.
- Coat the inside using bed liner which is chemical resistant.
- Seal the lid using weather stripping and toggle latches.
- Vent out top with piping to outside.
- Pass cables through using drilled-to-size notches just beneath lid and weather stripping.
- Use webbing tie down over entire box with anchors in the floor.

 

[gapper2]

LookinUp,
   I plan to build a vented 3/4" ply box. The inside of the box dimensions are given in the drawing.  I have AGM batteries so I am not so concerned with spills.  A hole drilled toward the bottom of the box will have a fan mounted on the side.  The shunt and neg bussbar will be supported underneath and mounted to the outside of the box.  If I were using FLA batteries, I would have vent pipe exiting side of box to the outside of van.

  The main disconnect switch and positive busbar will be supported. insulated and all main fuses will be mounted to the outside of the 3//4"box.  I think I will mount metal handles to sides of box which will be turnbuckled to van body.  The box will be approx 10.75" tall.

 

[gapper2]

Thought about it later.   Even though all circuits connected to pos buss should/will be fused.  A second ANL catastrophy fuse placed in between pos battery post and switch will give that warm fuzzy feeling.  Because  __it Happens.

 

[Vanada]

In case anyone is in the same boat, I'm seriously considering getting some of these split-gland cable grips which allow for pre-assembled cables. I just like flexibility and being able to reverse decisions if necessary: http://www.mouser.com/ProductDetail/Heyco/M3234GBJ/?qs=sGAEpiMZZMuGxYVy11yKKhYcuso0pppHUEyKptJXsys=

 

[Vanada]

Once again I need help making a minute decision: Thermal breakers inside or outside battery box?

Inside would keep them close to the battery but I'm not 100% sure on the safety aspect of having them enclosed with the batteries plus it will be very difficult to fit them all in.

Outside would be easier and neater but places them more than the recommended 15cm away from the battery and would involve unprotected wire running through cable glands.

Thoughts, pros, cons etc. would be appreciated! My box is shaping up well so it's all gonna be worth it in the end!

 

[SternWake]

I'd have no issues with them on outside of box, as long as the cabling is adequate for passing the maximum possible amperage they will see, and there is no possibility of chafing causing a direct short in the distance between CB and battery post.

 

[NomadMike]

Here's what I think I'm going to go with:
- Build a box out of 3/4" ply I have sitting around, butt joints and glue.
- Coat the inside using bed liner which is chemical resistant.

Just some info for any one interested, there is a paint that is used in the aircraft and marine industry that is made for this application. it is called [font=arial, sans-serif]RANDOLPH ACID PROOF BATTERY BOX BLACK PAINT[/font] http://www.aircraftspruce.com/catalog/cspages/blkfloatbtm.php

 

[user 37446]

Gads. No wonder people buy 12v AGM's... You still need to secure them but thats a lot more easily done.