Battery Vent Tube Questions

Discussion in 'Gen 2 Prius Main Forum' started by davecook89t, Nov 5, 2018.

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  1. davecook89t

    davecook89t Active Member

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    So a couple of weeks ago, I discovered that the AC Delco AGM 12V that I had installed by a trusted shop when I bought our Gen 2 did not have a vent tube. I called the parts department at my local dealer and was told that they did not stock this item as it was not part of factory equipment. I then went online to toyotapartsestore.com and ordered a Vent Hose for a 2007 Toyota Prius priced at $7.95, plus shipping. I few days later, I got an Email saying "The status of your order has been updated to On Order", but my credit card was never charged. After a few unreturned phone calls to the Sales Department, I have given up and purchased a few feet of 1/4 inch Outside Diameter vinyl tubing from Home Depot. The pictures of the tubing and my installation are attached.

    Is this likely to do the job in the unlikely event the battery becomes overcharged and begins to expel hydrogen gas? I believe I was able to push about 1/4 inch of the tube into the hole in the side of the battery. It seems fairly secure, but I guess it is possible that it could get jarred loose when I am traveling down the road. Would it be advisable to squeeze a gob of silicone sealant around the connection to the battery to secure the tube and prevent any gas from escaping around the side of it? I have pushed the tube into the side of the battery until it can go no further. Is that the wrong way to do it? Does it need to have some clearance for the gas to enter the tube from the battery or is there a relief valve that opens up in front of the tube when the pressure inside the battery exceeds a certain threshold?

    Thanks for any help any of you can provide.
     

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  2. PriusV17

    PriusV17 Member

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    My thoughts about certain plastic/vinyl tubes in general. If it gets very hot, it tends to bend and that bending can end up closing the passage way and defeat the purpose of venting hot air.

    So I would at least check that there are no sharp corner bends that can end up closing when really hot.

    You may also want to check into silicone tubes since they can withstand 450 F degrees of heat.
     
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  3. PriusV17

    PriusV17 Member

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    People are installing oil catch cans with clear plastic tubes. I would assume this applies to that as well.

    The bad thing about silicone is that is is not good with solvents.
     
  4. PriusCamper

    PriusCamper Senior Member

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    I got a whole box of old vent tubes... They're not necessary when you put in a higher quality 12v battery. In the best 12v for Prius there is no vent tube. High quality modern-day sealed AGM batteries don't need them. Vent tubes are a relic of earlier times when batteries were a higher risk. For example Gen2 Prius Hyrbid Batteries have a vent tube system for all 28 modules, but Gen3 prius hybrid batteries, which are the exact same modules have no vent tube system. They got rid of it because it was not needed.

    More specifically, the odds of a Prius overcharging a 12v battery are near impossible and the only way you'll need that vent tube is if your battery is damaged in a car accident but still functions and you keep driving the vehicle, which would be really dumb, but if you're Toyota you add the vent tube to protect yourself from the liability of people who are really dumb.
     
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  5. davecook89t

    davecook89t Active Member

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    Thanks. I did not know such a thing existed, but I see some online at a reasonable price, and will probably order it, unless anyone on this forum comes back and recommends not using it for some reason. I'm still curious about the actual mechanism for venting the gas. I'm guessing there is something that keeps the inside of the battery from being exposed to the open air. I'm hoping I haven't shortened the battery's life by sticking a tube into the side of it.
     
  6. davecook89t

    davecook89t Active Member

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    Is there no possibility that the DC to DC converter could malfunction and overcharge the 12V? I would like to think that, but I believe there are others on this forum who have suggested that may not be the case.
     
  7. Skibob

    Skibob Member

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    I can’t speak about the battery in my Prius but when I changed the battery in my BMW it came with a new vent tube and a little black plastic 90 degree elbow to put in the battery vent hole. If you can find one of those elbows you should be good.
     
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  8. davecook89t

    davecook89t Active Member

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    I wondered if an elbow might be necessary since there is not a lot of clearance between the battery and the side of its compartment, but the tubing seems to be stiff enough that it did not compress with the gentle bend I put in it. If the elbow has ridges on it that would help keep it from sliding out of the hole, it might be worthwhile putting one on anyway. I will look into that.
     
  9. PriusCamper

    PriusCamper Senior Member

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    Yes, that's why I said "near impossible." The scenario in which you state is pretty much the only way it can happen other than a car accident that partially shorts out the battery...

    But when Prius even has a voltage sensor on the hybrid battery cooling fan that throws error codes, (got a free replacement prolong harness because of it) there's probably more than one error code for bad voltage readings heading to the 12v battery. But again, when it comes to product liability, assuming the driver ignores the warning light, which too many drivers do, the vent tube is a last resort of due diligence for a litigious-minded manufacturer.
     
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  10. Stevewoods

    Stevewoods Active Member

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    Junk yard?

    I reckon the pirates will charge you $5 or so for the tube and the elbow, but....
     
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  11. MickyMatter

    MickyMatter Member

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    I've bought this BMW part for my Prius. It's fitting perfect to the new battery and the original hose.
    The BMW part number is 6 121 137 78 35.
     
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  12. davecook89t

    davecook89t Active Member

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    Thanks for the idea, but if adding an elbow from Home Depot and possibly ordering silicone tubing from an online source is sufficient to do the job, I will probably not go to the trouble of visiting a salvage yard and pulling one off a wreck.
     
  13. davecook89t

    davecook89t Active Member

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    Hmm, when I plug that part number into a Google search box, all I'm getting is references to a BMW forum in German. Unfortunately, I'm not as fluent in that language as you are in English.;) Thanks, anyway. I'm hoping what I have is good enough.
     
  14. PriusCamper

    PriusCamper Senior Member

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    Dude, these are basic small plastic pipe fittings available at any hardware store. Don't overthink it...
     
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  15. sam spade 2

    sam spade 2 Active Member

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    NO. Because a battery that is actually built with a vent, even one just for catastrophes, would have a nipple to connect the hose......NOT a hole. Your battery likely does not HAVE any venting and your hose is useless.
     
  16. MickyMatter

    MickyMatter Member

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    I've got this number from this German wiki:
    12V-Batterie – Prius Wiki

    I drove to the BMW dealer in the same street as my office, asked for this item and got it immediately for 2,11€. (They had it on stock.)

    ¯\_(ツ)_/¯

    How about this:
    61211377835 - Genuine BMW Connection Elbow 61211377835 | Turner Motorsport
    or this:
    61211377835 - Genuine BMW - Battery Vent Hose Elbow - Fast Shipping Available
    or this:
    BMW Battery Vent Hose Elbow - Genuine BMW 61211377835 | FCP Euro
     
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  17. Skibob

    Skibob Member

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    That is without a doubt a vent tube hole in the side view photo.
     
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  18. davecook89t

    davecook89t Active Member

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    That's the battery I have, alright. I was thinking there might be a hole on the other side as well, as some apparently have a hole on both sides, but running my finger along the top edge (I'm not able to see the other side at all), I don't feel any interruption to the smooth surface. All the same, I'm still wondering how it really vents. Looking at the close-up view of the hole, it seems as though there is a solid piece of yellow plastic preventing anything being inserted too far into it, although from the photo there is a hint that the solid yellow plastic comes to an end right before the top. It almost looks like my tube is too thick to allow any gas through such a small opening. Maybe as Sam implied, it is a fake hole, in which case I really am wasting my time.:(
     
  19. davecook89t

    davecook89t Active Member

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    It looks like any of those would help, but per my comment in #18, I might be about to abandon the whole project.
     
  20. Skibob

    Skibob Member

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    I cannot say for sure on your battery but the one on my BMW is more of an emgerency vent. The battery is pressurized and the vent only opens under extreme conditions. Such as jump starting a dead battery I guess. The write up does say it’s pressurized. One of the comments says the vent tube fits perfectly.
     
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