Do we really need the12 V Battery vent?

Mo

Most of the problems occur because people do things that drain the 12V battery.

 

I see some replies that the size of the Prius battery is overkill and then I see people warning not to leave the car accessories powered up because it kills the battery. Which way is it, it can't be both?

 

I would love to see an explanation from those that think the installed/rated Prius 12 VDC battery is overkill.

Running accessories with the vehicle powered up will not kill said battery...however, running accessories with the vehicle powered down...yes you will drain the battery...and shorten it's lifetime.

 

I did the same nearly 3 years ago, except that I connected the vent tube to it. $65, and no problems so far.

 

I'm confused—are you saying you bought a UB12350 and found it had a port for the vent tube? Or did you get a different $65 battery?

-Chap

 

SIGH.
Right answer, wrong question.

The fact that some owners don't know or don't bother to check the electrolyte level in a battery that needs it............should be all the MORE reason not to get one like that.

OR......what does the fact that some owners are completely ignorant about battery maintenance have to do with the rest of the discussion ??

 

I modified it slightly, so now any vented gas is directed into the Prius vent tube.

 

Looks good to me.

 

My Aunt owned a 1969 Volkswagen Bug. I was just a kid, but I still remember her calling my parents one morning upset because it wasn't starting.
My Dad asked her if she had checked the battery.
My Aunts answer was 'What Battery?".
She wasn't very mechanically minded, and had heard that VW's were "different"...no radiators..etc, so she just assumed it had no battery and had owned it for years and never even knew it existed.

We assumed that when she took it for service, mechanics were checking it for her. But it came as a big surprise to her when she discovered it even had a battery.

 

Turns out we do have some data after all, in this post by AHetaFan, from way back in 2014, even. I just hadn't stumbled on it until now.

Measured 60 to 70 amps initially into a 60-to-70-percent discharged battery (the post doesn't explain how that determination of percent discharged was made). Slightly under a kilowatt (at around 14 volts), or about a horsepower and a third.

Now, with anything like a sustained current of that magnitude into a battery (such as with a shorted cell), I'd expect substantial and noticeable amounts of heat and outgassing. That's nearly like having a regular household space heater tucked in the corner of the trunk.

-Chap

 

Why do I have to keep repeating this!!

ALL lead acid batteries convert -some- of the water in them to H2 and O2. Because of this they loose water. There are a few batteries that have a "recombination system" inside that combines the H2 and O2 and turns it back into water. You can't afford those for a car, in general though they are available.

Just because you have an "AGM battery" doesn't change this physical fact. An AGM battery is just a lead acid battery where the electrolyte is held in a glass mat. What this does is keep the electrolyte from leading badly if the case is cracked and it helps to support the plates inside in high vibration environments. It DOES NOT change the fact the battery is still a lead acid battery. The basic chemistry does not change! By messing with the chemistry (ultra pure lead for example) and the design of the battery (cell interconnects are kept out of the electrolyte as much as possible) you can -reduce- the hydrolysis, but you can't stop it entirely. This is why all lead acid batteries loose water over time. If the design is well done, and you are lucky, the water loss isn't the reason the battery fails, it fails for some other reason (crushed in accident, sulfated by over-discharge, cracked by freezing, posts damaged by monkey mechanic rather than technician, etc).

As hinted by Chap, the H2 generated in normal operation is not enough to worry about, even in a closed car. BUT, if "something" happens that isn't "normal" H2 generation goes way up and you could have a problem. I doubt there would be an explosion problem, a car has too large a volume for a battery to fill to explosive concentration in a day or two. You would have a smell problem, with SO2 and H2S gas.

Oh, and even though you may not be able to find the vent hole, there is one, or you have a bomb!

 

Probably because it is NOT true.......at least most of it.

AGM batteries DO recombine the gasses produced by electrolysis under normal conditions.
Those designed for use outside of the passenger compartment (most of them) do NOT have a vent tube because, under normal conditions, one is not required.

If you care about this SO MUCH, then you need to research it a bit more and get your story straight.

 

Correct, those in open atmosphere can vent willy nilly without build up, only those enclosed by the car need an external vent. But AGMs all vent.

Should you think only Prius have this issue, look at this battery replacement.

http://www.m5board.com/vbulletin/e60-m5-e61-m5-touring-discussion/302977-2008-e60-m5-battery-replacement.html

 

Under normal operating conditions, they positively absolutely do NOT.
That is why they are called "sealed".

Now.....there is some kind of an emergency "pop-off" vent on them but it never operates IN NORMAL OPERATING CONDITIONS.

 

There are plenty of batteries available now, dimensionally compatible, meet the spec's, and have the (compatible) vent. And Toyota in their wisdom has a vent tube. Just get something that's compatible?

 

Well Sam, I guess you'd better publish a paper so all my instructors in advanced power mechanics and the PHDs in chemical engineering can learn from you.

AGMs do vent in "normal operating conditions", and that is why there is a vent tube. They don't vent much, but they do vent. It's also why both Prius batteries I have replaced were down on water, and it's why all the "sealed" ones have "pop off" valves, so they don't explode. They don't vent much, but they don't recombine. To do that you need a catalyst. There isn't one in any but the most expensive batteries. I'm talking of at least double what Toyota wants for the Prius 12V.

 

I prefer for me and my passengers to be safe even in unusual situations.

 

About 10 minutes with a simple Google search is the only research time you need to dispel the mis-information you have about AGM batteries.

Unless you just want to continue this pointless pissing contest.

MOST AGM batteries do NOT have a vent tube. That applies to cars, trucks, motorcycles, boats on and on.

I quit.

P.S. I was wrong. It only took about 5 minutes......including the time to read the first page of information.

Absorbent Glass Mat (AGM) Battery Information - Battery University

 

Sam, something we can agree on!

Most batteries just vent willy nilly as they are under the hood, only batteries designed for the interior of cars have a tube.

 

AGMs do not vent at all.
Except for the emergency pressure relief valve, they are SEALED.
I quit. This is ridiculous.