sportlineguy

I have found a clear plastic hose/tube near the battery that I think is the battery vent but it is not hooked up as the current battery is sealed. Should I replace it with a vented battery or another sealed battery? Pic should help sort this out.

It is on a 2001 996.

Thanks

Goldenwarrior1

It is the battery vent. Someone replaced the battery with a non vented battery. Not a good idea IMHO...

jyoteen

that battery is vented. See the nipple in the back (middle). Just the vent hose isn't connected.

Goldenwarrior1

You have better eyes than me, I missed it!

fpb111

Gw,
Curious, why not use a "sealed" battery? Seems like an AGM or Gel battery would have less chance of sloshing acid into the nooks and crannies of the bulkhead.

sportlineguy

The battery is sealed and no vent - looks like possibly a nipple out the back but nothing there. When I replace it will look at both vented vs non-vented. Is there really any difference overall?

Goldenwarrior1

When charging a lead acid battery a portion of the charging current, that which is required to maintain 100% percent state of charge, will electrolyze water thus generating free oxygen and hydrogen gas to be vented from the battery. The mixture of the gases are explosive which is why they are vented from the car. VRLA (Valve Regulated Lead Acid) and AGM (Absorbed Gel Mat) batteries are sealed and therefore do not require servicing or venting. If you use a sealed battery then you do not need a vent tube. Because the wet cell lead acid batteries are the cheapest I suspect Porsche engineers went that direction simply to save money. Kind of like the infamous IMS bearing...

fpb111

I have been very impressed with the AGM batteries. I had them (two for early 911s) in my '72 hot rod for 12 years with no problems. I use a battery tender during storage. Both of the early cars, 1970 & '72, needed new battery boxes welded in due to battery acid corrosion.

I have a 1998 BMW R1100RT that has a 10 yr old Westco AGM in it. Still starts that high compression twin with little problem.

My 2003 C2 Cab needed a new battery when I bought it so I got a Braille AGM. We will see if it gives similar service in the newer car.

fbgh2o

I discovered this one today while changing the cabin air filter. I guess it is a battery vent hose, but I am not sure. It appears to go exit into the wheel well and has a 90 degree elbow on the other end.

Could it also be a sunroof drain?

street rod

Looks like the battery vent. Mine has the 90 degree on the end also. My new battery had a differnt type of vent hole and I had to replace the elbow with a different fitting.

Goldenwarrior1

Looks like a battery vent to me and doesn't appear to have been used for some time! Your sunroof drain is larger diameter.

relinuca

I think the battery vent hose definitely serves a useful purpose in the case of vented batteries, which most of us have. To wit: if you slightly over fill the cells with distilled water (which is easy to do), then the excess will be expelled via the vent hose to the ground...out of harm's way.

In other words, the venting function applies to both gas/fumes and fluid.

relinuca

SSST

AGM batts should do fine in these cars. I use them in my boats and they will take a heck of a beating.