There is no risk of gas release unless battery is overcharged. Mercedes is a regulated system, there should be no issue unless you're trying to jump start your auxillary battery (which is pointless).

Even then, since most of the hydrogen is absorbed, the little amount that would get released under that rare circumstance is not enough to blow anything up. You would need hefty build up and ignition to have anything remotely effective.

And once again, the lower trunk isn't completely "sealed off" so that wouldn't work either.

Sending links of hydrogen bombs doesn't help the argument. It's not that I can't see your side, it's just that it's not a likely event.

Well then let's just agree to disagree... The stoichiometry only needs to be 4% for an explosion, but you do you, don't let me stand in the way.

That's fine! I remember hearing once, a boardroom had 10 people. It was the 10th person's job to disagree with everything the other 9 agreed on. It's how we ask questions people ignore or look deeper into.

Like I said, I will report my findings over time.

Ope, ya edited the post on me. Had to go for it huh.
My background is in biochemical sciences - I think I'm familiar with a thing or two 😉

Like I said, you do you...

From what I recall OE batteries are made in Thailand.
Watching the comparison video, looks to me like they used MB molds to make the cheaper duplicate.
That would make it OEM battery.
Than if the manufacturer design the battery with no vent, I wonder what is the issue here?

Seatbelts are only intended for extraordinary circimstances too. Probably never need them though. Of course, when you do need it is not the time to try to put it on.

um, someone who copies the molds is not the OE unless they are the actual vendor who made the batteries for MBZ.

and if they'd copied the molds, they'd have a vent. they don't (actually, I thought I saw a little hole in the center of the top).

btw, someone above said AGM is the same as Gel, thats not actually true. AGM batteries have a glass mat holding the liquid sulfuric acid electrolyte, while Gel batteries have a paste electrolyte made from the same sulfuric acid and powder glass. The two types also use slightly different 'doping' in the lead plates, with differing percentages of alloying metals like antimony and tin. and two externally identical looking AGM's could have quite different plate constructions inside, some optimized for short high current discharge like a motorcycle starter battery, others optimized for standby use with trickle charging and moderate current discharging such as a standby battery for a burglar alarm, and yet others for deep cycle high output use like a computer UPS system. these types are visually impossible to tell apart, you need the spec sheets for the manufacturers part number, such as https://eu.industrial.panasonic.com/...nteractive.pdf (my favorite AGM vendor, however they don't seem to have a 12V 12AH battery with the correct terminal type). btw, page 25-26 of that PDF discusses AGM failure modes and related safety factors.


(did I mention I'm a retired engineer, both software and electronics?)

Re-examined rear compartment, has 2 holes that lead to bottom of the car, as well as the rear plastic from the inside has space along the width of the rear that exits through the rear bumper. Since the only concern is gas if for some reason there is overcharge, there is room to escape. It will not build up.

Copying mold won't make it OEM, you'll actually see several batteries in this generic shape. It would have to be a direct producer of the battery. Same goes for large batteries.

​​​​​​

Who was talking about copying the molds?

you were.

anyways, even if it comes from the exact same factory, if its not made to the OEM specifications, it is not 'OEM'.

Looks like there are pressure release valves in the trunk as well, they only let air out but not in.

Anyways, do whatever you're comfortable with. The video can also help just demonstrate replacement.

I never said that I don't do much of the regular maintenance myself. Oil changes with an extractor. Brake fluid with a pressure bleeder. Spark plugs following Sr. Leighs tutorials. Brakes and rotors.
I have lots invested in tools and enjoy the work and saving the labor costs.
BUT, I do not skimp and save on parts.
Just sayin

Since you brought it up...
You know that hydrogen gas is lighter than air, right? Holes that lead to the bottom of the car won't do much except allow the air that gets displaced (from the admittedly unlikely influx of hydrogen gas) a place to go. Now if it was propane (heavier than air) we were talking about, those 2 holes might be an asset.


I love it when threads go sideways.

You Sir have a problem with English comprehension.

Trunk vents have duck beak valves and carry whole air from cabin air exchange.
Did not follow it on W212, but previous models had ducting on rear shelve that was letting the air to go to the trunk and than out behind rear bumper.

Gentlemen, there is no need to insult each other over these money pits.

While we find ourselves stuck in the same boat, we can share our points as adults and respect each others different priorities.

The common thing we generally dislike is holding short straws ... To each is own choice & vantage point.

The OP video is most excellent, in contrast with replacement AUX AGM.
👍

Yes, these holes are near the upper metal on the rear compartment, above the batteries height. They lead to the bottom of the car, phrased badly I guess.

Well said, I actually saw a video yesterday that said "experts disagree on..." The same topic we are all here disagreeing on haha.

Remembering similar discussion(s) on a seemingly lesser forum a few years ago… First let me say I prefer a battery that is vented to the outside of the car. I surmise that with the passage of time and several generations of ownership from now; cost will move to the forefront. The vent tubing will be long gone and probably supplying air on an Eight year olds' aquarium.

Any technical reason to prefer vented battery v/s no vented?
When this become religious-oriented dispute, when battery was design with no vent, that means it is not needing it and it is not venting. End of the story.
As to checking if the aftermarket battery was made from MB molds, or new molds - OEM manufacturers remove logos and part # from original molds when they go on secondary market.
Original batteries have sticker, so no molded logos, but if that is the same mold- it will have a mark on new product where older product had a vent.
OP can you check it to fulfill our curiosity?

I agree, I always spec Panasonic batteries for back-up on my process control panels, I also think their power tools are best as well, but that's an opinion. Love my Panasonic cordless drill, my fifth as I gave them to my children as they left home!

Dear Sir, in post #32 A contributor posted a link to a manufacturers page that answers your questions I believe correctly.

AGM risk if overcharged = gassing off. That is stated by all good battery brands.
I think MB decided to be extra safe because potential law suit may arise one day, if ...touch wood... somehow over charging occurred and minor accident came about and a smart investigator decided to
use "NO VENT AVAILABLE" as his technical finding, MB may end up loosing the case. Its only a few extra low $$ for MB to prepare the vent ahead of time and command their battery supplier to make that vent hole.
Anyway such precaution is a good engineering.

Mine is FIAMM brand battery, btw.

Simple reason why a fuse is installed on circuits. If we are all 100% sure Uncle Murphy Law will never come to town, probably we can do without a fuse.

The only link I see in the mentioned post is sale pitch for Panasonic batteries.

When I agree that there is not such thing as too much protection, 1 of main reasons for installing AGM batteries in passengers cars is more safety.
Seem to me several members fail to comprehend that AGM batteries by design don't require vent.
Check Wikipedia for more
Bare in mind W212 were originally design for flooded batteries, where vent in fact is needed.

that PDF did start off with high level overview of the Panasonic AGM battery line-up but it also has full tech info on every feature and part number and option, along with spec sheets of every specific model. as I said, around page 25-26 of that ~150 page PDF discusses safety. the key point is that not all AGM's are the same even if they have the same voltage and AH rating... they make different versions for different use cases, standby power, deep cycle power, motive, starting batteries, etc.