the 4 year old AGM main battery in my 211 CDI is vented and is connected by a tube to the world outside the trunk.
Just an observation.
YMMV

 

That is what I said above - Thailanders improved Mercedes design.

 

how does a cheap generic battery not having a vent attachment 'improve' the design ?

That MightyMax battery IS valve regulated (*all* AGM batterys are VRLA, Valve Regulated Lead Acid), hence has vents internally, that vent into the space under the top cover if the battery goes over-pressure, which WILL happen if its over charged or discharged at too high of a rate, or a cell fails, or whatever.

That MightyMax is a clone of a Yuasa YTX14-BS (note the same part number, which is a common motorcycle battery size. The Yuasa even says VRLA on it. https://www.yuasabatteries.com/battery/ytx14-bs/

 

" Cheap" has different meaning in English, so
the "lower priced" battery is true AGM battery as those don't require venting.
MB design require venting, meaning it is not true AGM aka it is cheap design.
Clear enough?

 

AGM batteries are 'valve regulated', and those pressure release valves outgas under failure level conditions, such as a failed alternator regulator overcharging the battery, or a shorted cell causing the other cells to overcharge and boil.. which part of this don't you understand ?

the mercedes battery is a true AGM, absorbed glass mat.

 

Evidently Wikipedia and other publications disagree with you.

 

oh?
https://en.wikipedia.org/wiki/VRLA_battery
VRLA battery types include AGM and Gel. both have pressure release valves.

https://www.autohausaz.com/pn/MB-0009829608
the Mercedes W212 trunk battery is an AGM.

 

I wonder if the 12v in dash aux has a vent

Since we're on this topic

 

just looked in WIS, and while the procedure for the ECO start/stop battery in the trunk does have a vent hose, the smaller battery in the dash does not mention any step to remove or replace a vent hose.

 

I think we might be back to square one then - this is even closer to the passengers, so I find that odd. Doesn't appear to me as well for it to have one.

 

well, its a much tinier battery, and those are less likely to outgas? I dunno, wild guess.

 

No it is a different design, more like a alarm system battery, 2 ampere hours, just for shifting transmission into or out of park, kept fully charged and used for nothing else. the battery in the trunk is used for start stop and brake hold I believe so goes through constant charge-discharge cycles and is 200 ampere hours,100 times bigger, so needs a vent tube to off-gas. comparing these two is apples and oranges.

To all my friends on MBW, do not put a non-vented battery in your passenger compartment, for the rest, it will give us an opportunity to test Darwin's theory of natural selection. LOL.

 

Man, I'm not sure what's in the water in Ohio...

Once again, there's THOUSANDS of people running these, so if it was a problem we would have seen a LONG TIME AGO that there were Mercedes blowing up left and right.

Your argument is it's a smaller battery? You do realize even this one isn't a full size battery? There's cars with full size batteries in the trunk. Both are AGM and you can bet that BOTH are getting recharged, both are 12V, a full car size battery is 60Ah+, this one is 12Ah, the dash is 1.2Ah.

It's simple - DONT BUY THE BATTERY IF YOU DONT LIKE IT. Why's it so hard to move on? Go enjoy your stock E350. Watch out, if you don't put OEM spec tires, they might blow up on the road.

 

Condescension noted and dismissed...

 

Heh, says the guy hoping to utilize Darwin's theory...

​​​​​​Typical 50+ y.o. afraid to try new things, struggling with smartphones.

 

I don't want to get involved in this cat fight, other than to suggest this Auxilliary battery business -- whether in trunk or dash -- is nonsense on it's face. More debate regarding safety than the topic is worth.

Months ago, there was a thread on the safety of "covering" the trunk battery with padding to cut down road noise. Oh, no, can't do that, cause that will cause the battery to overheat, or it will limit the battery's ability to "breath" or vent it's Hydrogen gasses.

Not to mention that the battery is covered with the hard trunk liner covered in carpeting on every model... Not to mention that some models even got an additional, molded cover specifically for the battery, both designed, manufactured and approved by Mercedes-Benz lawyers...

Starting to think this battery vent hose business is just another "liability hose." If there really is a safety issue with the auxilliary battery, then it should have been installed outside the passenger's compartment areas... Ummm, in the engine compartment, where it really belongs, frankly.

 

I appreciate this, as I've been trying to keep it this direction, but apparently it's difficult to avoid coming back for some people.

Good insight. Several batteries at autozone, for example, don't have vent ports, and they are full size replacements including ones that sit in the trunk. I have yet to hear of people's cars exploding.

 

no vent


No vent
2 different brands right there, guess their cars blow up

 

Another thought...

Battery manufacturers have been working for DECADES trying to seal these batteries, to keep internal fluids from evaporating (in lead acid batteries). Longer battery life, no maintenance, fewer battery explosions while jumping, yadda yadda yadda...

Now it's imperative to create another hole to the outside atmosphere to let it vent? Really? Make up your mind...

 

My disagreement mainly lies with the fact that the trunk will build up with "so much hydrogen" that it will easily cause an explosion.

Looking at the chemical equation, whatever isn't absorbed by the glass mat that's converted into H20 to be reused, release will be minimum if at all under the *rare* circumstance that it's overcharged. In addition, the fact that it's <1/4 of the reaction of a typical battery, the hydrogen to oxygen mixture will not be even close, even ignoring the fact that there is open ports all over the trunk. Even a full size battery will have a hard time achieving this unless it's consistently getting overcharged, which would definitely not be happening under a cars regulated system.

Then, you need an ignition regardless. Go light a match in your trunk?

If it was a problem, it would be *illegal* to manufacture batteries without a vent port. Simple as that. They made headlamp washers mandatory under law for HIDs at one point, you think they wouldn't for exploding batteries?

 

It is not possible to fight religious and other believes, so if somebody say AGM battery has to have the vent - let them live with that.
Engineers and user of AGM batteries, where they operate on their sides say otherwise, but the believers are not going to change their mind.

 

das ist das ... da VENT PORT!

this battery looks very much like a good old conventional non-AGM battery. The fact it is coupled to a temp sensor mounted on (-) pole, makes it look like a MAIN battery, not a small AUX.
IT DOES HAVE A direct VENT PORT... not the type that can be routed outside through the plugged hose of discord 😏

I am going to venture this is not an original equipment. This battery application is for non-enclosed vented environments...ie. engine hood not trunk. 🙂



unlimited charge rate


QUESTION:
What controls the recharge rate of our AUX Batt.???
I'd answer: not 100A fuse, nothing does !
AUX is charged in parallel with MAIN... rodeo style😅

What do you think??

 

I think if engineers argue over this then what are a bunch of Mercedes Benz owners doing bothering about it on a forum to be honest.

So then what's that leave the charging rate of the in dash aux battery?

Because that's a much *much* more enclosed space, and the hydrogen has nowhere to go...if it pops off, it'll activate your knee airbag in the process, causing you to maybe accelerate into an accident. LaWsUiT?

 

Wow. I have decided to now let my dealer do all my service at whatever price they demand, so I don’t die in my Mercedes. Thank you all for this great PSA.

 

Lol guys, I think we should just call it here.

There's perfectly accurate statements on both sides of this argument, at the end of the day, just do whatever you're comfortable with.

If people weren't trying to learn or try new things about their vehicle platforms, forums wouldn't exist. Simple enough.