SCMike

In doing a bit of battery self-tutorial, I took a closer look at the OEM battery in my 2015 Cayman (has auto start/stop). The battery is made by Banner in Austria (but it looks a lot like the old Moll case style - except the area where the acid "fill" ports would be on the Moll is here plastered over with labels). I assume that this is an AGM battery due to the stress of the start/stop (which I always have off anyway). The Banner website says to never open the fill ports on the AGM battery (duh).

My one real question is: am I seeing straight that the AGM battery has no venting system? No signs of the venting tube like on my 987.2, and the vent ports on the battery seem to be plugged. I guess the AGM does not need to be vented?

Anyone with a late model 981 see the same absence of the battery venting tube?

nxfedlt1

If it really is an AGM, there is no vent "tube". If you can post a pic, it will be easy to tell if its an AGM or lead/acid.

SCMike

How do you tell if it's an AGM? Here's a photo of a different battery from my other battery thread. To maximize confusion, this battery is naked of all identification stickers and may have a trojan vent tube. Is this an AGM? Thanks!!!

nxfedlt1

that is not an AGM. AGMs don't have the standard vent tube and those circle plugs look the caps to the cells where you would add additional acid when and if the level gets low. AGMs don't have those access holes, atleast none that I have ever bought, and I buy them fairly frequently across all of our boats.

SCMike

Unfortunately, the Porsche OEM AGM battery in my 2015 Cayman (not the one in this photo) DOES have have the vestigial access holes where the vent tube *could* be hooked up, one on each side of the battery near the terminals - the holes are just plugged up and not used. So that vent hole position does not necessarily distinguish between AGM or not on Porsche OEM batteries.

Also those circular plugs on a flooded acid battery are usually notched on top so that the plug can be unscrewed to add acid/water, and the stickers applied to the battery top are positioned so that there is clear access to the screwed plugs. These smooth plugs in the photo do not seem to be designed to be removed and could have been normally covered by the top case stickers (which are totally absent here) on an AGM battery. On the for-sure AGM in my 2015, these plug locations are not even visible, being under all sorts of applied stickers that are not meant to be removed.

I wonder if the Porsche OEM uses the same basic outer casing for both battery types and just varies the guts and caps off the redundant openings. So...I still remain confused as to this pictured battery's identity in my 2011 Spyder. Maybe the top casing stickers are the clue as to AGM or not - they either cover up the area at the top of the cells or not. In my case, the battery pictured is lacking any top casing stickers, so no clue there.

My apologies for any confusion due to my conflating the two battery threads that I have started. This posting has flipped back into the quest to understand the battery in my 2011 Spyder (please see my other thread - Whosis?).

JCtx

As I mentioned, certain markets might require lead-acid batteries to be vented, so the provision for venting has to be there. Remember wet-cell, AGM (absorbed glass mat), and gel-cell are ALL 6-cell, lead-acid batteries, so the same casing could be used for any type. All that changes is the 'electrolyte' type.

As far as the vented battery pictured above, it could be an AGM or 'maintenance-free' wet-cell. The stickers were removed by somebody, as all batteries always have them from the factory. Without a part number, you'd have to call a dealer with car's year and model to find out. But I'd assume it's a wet-cell. Most manufacturers are turning to AGMs, due to being much safer for the cars (no acid-related warranty claims, and in case of accidents), longer lasting, and can be installed anywhere.

sjfehr

Flooded (wet-cell) lead acid batteries off-gas during charging and require occassional topping off with distilled water. If you don't have a vent tube, your frunk will fill with hydrogen sulfide and hydrogen gas, neither of which are desireable.

Valve regulated lead acid batteries like AGM are sealed and pressurized and do not normally release gas. However, as the name implies, they do have valves and if internal pressures are too high, can off-gas hydrogen. If this happens, you can't replace the "lost smoke" in an AGM and the battery is junk and you need to replace it. But by the same token, you really don't want that hydrogen gas in your frunk either; it's not an issue for cars with open engine bays as the gas will safely dissipate without reaching dangerous concentration levels, but Porsches and many other cars with batteries in sealed compartments need the vent ports to ensure the gases are safely dissipated. It'll happen during overcharging; don't ever overcharge an AGM battery.

So, the lack of a vent isn't a HUGE problem, but it's still a risk you need to be aware of. Since our cars pull fresh air for the vents from the battery compartment and the (odorless) H2 is usually accompanied by (definitely not odorless) hydrogen sulfide, you should smell it pretty quickly and (hopefully) be able to take action before concentrations become dangerous.