For my 73 Dart I made a custom, air tight box that ventilates through the bottom of the box, if anyone is curious and would like instruction or maybe pictures I could provide some. The only problem that I have found with the box is that it takes a long time to put on the lid

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My car may be slow to sixty, but at least it's been reliably slow to sixty for more than thirty years.

Sounds like a neat idea, but shouldn't vent holes be near the top of the box since thats where the battery vents themselves are (and escaping gas rises as well) ?

you are right about gas rising, but I don't won't to vent through the top because it will go into my car, which is not what you want. I figure that if I'm driving air will be forced to circulate into the holes, and if the gas collects enough it will start to go through the bottom. I also got a sealed battery so that really it's not too big of a deal unless I have an emergency and must use a normal battery. Do you have a trick for venting through the top, because I agree that would be much better but I just couldn't figure it out. I did think of a way that would work very well for driving but would be way to much work for good ventilation. Make a box that fits behind your wheel well and use the wheel well to force air into the box, on the other side of the box you can make some duct work thing so that the air has somewhere to escape. Either way, as long as it's vented somehow and is a sealed battery it should be safe, I personally don't want to test it with an unsealed batter unless I absolutely have to.

A VENT SHOULD BE AT THE TOP OF THE BOX, TO RELIEVE HEAT AND MOISTURE. BY ADDING A VENT AT THE TOP OF YOUR EXISTING BOX YOU PROVIDE CIRCULATION, WHICH IS THE KEY. SHOULD YOU CHOOSE THIS NOW, (WITH THE BOX INSTALLED) THE MODIFICATION IS NOT SO DIFFICULT.

NATURALLY, THE BATTERY MUST BE REMOVED. ALMOST EVERY DART HAS A RUBBER PLUG AT THE BOTTOM OF THE TRUNK WHER IT MEETS UP WITH THE QUARTER PANEL. THIS CAVERN IS WHERE ALL KINDS OF STUFF, (LEAVES, DIRT, OIL CONTAINERS) COLLECT. LOOKING FROM THE BOTTOM, YOU WILL SEE IT AT THE REAR NORMALLY. YOUVE PRETTY MUCH DISPLAYED FABRICATION ABILITIES BY MAKING THE BOX ITSELF.
YOUR GOAL NOW IS DEFINETELY VENTILATION, EVEN THOUGH YOU UTILIZE A SEALED BATTERY, HEAT AND MOISTURE WILL DEVELOP AND THAT IS TO BE AVOIDED. A TOP VENT FROM THE BOX TO THAT RUBBER PLUG IS HIGHLY RECOMMENDED. REMEMBER TO USE NON CONDUCTIVE TUBING AND INSTALL THE "EXIT" END THROUGH THE PLUG THEN SEAL IT WITH SOMETHING SUITABLE.

IVE USED BATTERY BOXES BEFORE AND WISHED ID THOUGHT OF THE BOTTOM VENT BEFORE. COOL AIR ENTERS THE BOTTOM AND PUSHES THROUGH THE TOP. AS FAR AS SOLVING THE STANDING STILL ISSUE, MY GUESS IS, WITH A PERFORMANCE MOD LIKE RELOCATING THE BATTERY, YOUR CAR ONLY SITS STILL WITH THE ENGINE OFF. YES?

IM PROBABLY GOING TO JACK THE BOTTOM VENT IDEA. DONT HAVE PAY A ROYALTY DO I ?

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IS 40:31 gets me through lifes challenges.

Glad I could help you with the bottom vent idea, I'm going to jack your top vent idea but with a modification. I sitted my battery directly behind the seat and so if I were to use a ventilation tube to the plug I have it would have to be at least 2 feet, I'm planning on making my trunk look pretty this summer so I don't think two feet of duct work is going to help me achieve that goal. I upholstered my battery box so I'll have to cut through fabric but from the top I can stck a ventilation tube that goes to a hole I make for the tube(I'm not a stock sort of person). Thanks for the ventilation idea, I wish I would have thought of that originally, I would have made built in duct work on the box.

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My car may be slow to sixty, but at least it's been reliably slow to sixty for more than thirty years.

Oh yeah, I'm strange, I actually did the relocation to test my welding and upholstering abilities. I also cringed when I saw my engine compartment, though I do plan on making my engine stronger, right now I'm working on looks and liveability.

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My car may be slow to sixty, but at least it's been reliably slow to sixty for more than thirty years.

You can always use your defogger fan and duct to vent the battery box. I would shy away from the wheel well because of dirt, tire dust and rainwater forcing its way through the tube. Of course you want to discharge any gases out of the body. If you dont cringe at cutting holes I would force vent it between the trunk floor and the gas tank, which is out of sight and protected from slung debris. If you want you could plumb a duct from the top of your battery box to a flange in the floor, and then run a steel pipe from the floor to the outside, at a departure angle of say, 30 degrees, and cut an angle on the end of the pipe to resemble a tailpipe, this would give you an extractor effect at speed and use the venturi principle to siphon the gases out of the box. Even a 1" pipe would be adequate. I wouldnt worry about accumulation of hydrogen gases at a standstill unless you idle your car for hours on end and your voltage regulator is shorted.