ok so yesterday i attempted mount a battery box in the trunk of my s13, (almost necessary when running fmic). so i got this nhra approved box that has 2 long *** threaded rods that need to bolt in from under the car. So of course afterwards i find out there's like 1/4" between the fuel tank and trunk..

Anyway the box has a vent tube to the outside to vent off battery vapors. When and why do you get battery vapors? What kinds of vapors are these? how dangerous are they?

Ok so optima batteries are sealed, you can mount them wherever in any orientation you want. i understand that. But at work (mercedes) i sell batteries all day long. most of our batteries have vent tubes attatched directly to them. The battery i pulled out of my s13 (pictured below) has no provisions for a vent. do i still need worry about vapors from this battery?

 

That isnt a sealed battery, sulfuric acid = bad
Sulfuric acid - Wikipedia, the free encyclopedia


From what I know the battery relocation box should be sealed the vent tubes vent the fumes inside the box to the outside. Thus keeping you from being dead

 

Seeing as how a Miata is not even close to the definition of "air tight" I don't see what you have to worry about.

Before anyone jumps on me, find me ONE example of a Miata that has blown up because of a non-vented battery.

 

Yeah but the Miata battery has vent tubes built in..

I had an Odyssey 680 (the small DIN-size one) in the trunk of my CRX, it worked great and didn't need to be vented. I'd recommend going that route.

 

He is putting the battery in an s13, not a miata. not that that matters..
I would also recommend a sealed battery of some sort.

 

Ever notice the warning labels on a battery? They can produce an explosive gas, Hydrogen.

 

You want SLA. Endo story.

 

Agree with everyone else, get a sealed unit. As to the need for a vent on the old ones- they do produce nasty explosive gasses when charging, drilling a hole and running the tube is easy. It is exceedingly rare for one to explode, but when they do its an absolute mess.

 

The miata comes with a semi-sealed battery from the factory.

as to the OP, I would go pick up a sealed battery just for safety reasons.

 

got the box mounted today, just need to run the power wire and i'm done

 

Woah. Thats a nice battery box. Cost?

 

got in on ebay $50 shipped, i really didn't like the idea of those cheap plastic ones with the nylon strap

 

So did you need to drop the fuel tank? I'm going to be installing a battery box in our S13 trunk soon too.

 

no that's why i did it on the drivers side. the rods go through right above and next to the exhaust where there's enough room to work. I would rather install it on the passenger side for better weight distribution but i'm pretty sure there wouldn't be enough clearance for the nuts on the end of the rods between the tank and the trunk without welding them right to the trunk. Actually it looks like the tank is stapped right against the trunk pan with some foam in between them. It may be easier if you've got a hatch because you'd be able to install the battery up closer to the seat and still be able to drop the battery down into the box, can't do that with my coupe. It's pretty solid so i'm not worried about it, and it's vented right behind the box too.

If you don't mind spending some money you can get some small batteries that can mount sideways on the battery tray and fit with the intercooler pipe running through it. In fact many people use miata batteries. I'm running a 3" cold side pipe so i'd be forced to get something smaller like an oddyssey or braille or whatever small battery i can find. Some people even use lawn tractor batteries but i'd like to have a full size battery for dead of winter starts. Plus i thought i could better use the money somewhere else on the car since the battery i already have is fine and i already had the wires and stuff necessary to do it this way

 

Ok thanks for the info. Yeah we have a coupe too so it might end up going on the drivers side like you did.