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I have run optimas before. I am aware of the small vents on top. This wasn't what I was confused about.
What I am still confused about is that it seems that C7s have batteries in the passenger compartment, yet are not sealed and vented out. Sure there is a small vent tube out of that area, but it is not like a gaskets and sealed off box like other FLA battery compartments need when inside the passenger compartment. Unless of course I am missing something.
^^^
Yep, as I defined in post #38 both the OEM and The AGM replacement I used had a vent hole in the top where the hose that goes out the bottom of the battery compartment is located. It's to avoid an accumulation of hydrogen (about 6% in air is a potentially explosive mixture) does not need to be sealed for breathing etc.
This pic from my Street Rod (built 20 years ago) where I didn't bother with any vent with the Optima AGM batteries. Started with Red Top switched toYellow top. It will only vent if overcharged and gas pressure exceeds 2 to 3 psi. I don't overcharge! Top pic, as delivered to the Interior shop and bottom finished. With tubbed rear and set back 8.2 Liter engine no room in the sedan for a rear seat so made a "sound wall!"
Ok, so to add more clarity, the battery itself vents out the car via a tube, but the compartment where the battery is located is not sealed and vented?
I am familiar with the overcharging situation with AGM and the risk of hydrogen gas. Really just want to fully understand the sealing and venting of the C7 and its battery.
(Side note, I am building a custom resto mod camaro and I may use a C7 battery for the build. Trying to decide if I go yellow top and leave open, or sealed and vented FLA battery. There really isn't room for a big battery box and conventional FLA battery)
Ok, so to add more clarity, the battery itself vents out the car via a tube, but the compartment where the battery is located is not sealed and vented?
I am familiar with the overcharging situation with AGM and the risk of hydrogen gas. Really just want to fully understand the sealing and venting of the C7 and its battery.
(Side note, I am building a custom resto mod camaro and I may use a C7 battery for the build. Trying to decide if I go yellow top and leave open, or sealed and vented FLA battery. There really isn't room for a big battery box and conventional FLA battery)
If building a boat, would have the box sealed and vented! But didn't consider for my Street Rod. Good luck with the Build!
I started with a standard Optima and It was discharging pretty quickly, so bought a Yellow top. Turned out my thought that a 20-mile drive would charge the battery was wrong! The C7 and C8 shut down all significant power after 5 to 10 minutes. In fact, someone just measure the parasitic current draw in a C8 and it was only 15 milliamps. Although I only drive 3 to 4 days a week (been retired 20 years) it's about 50 miles round trip to town so very seldom use my charger.
After I replaced the Red Top with a Yellow Top Optima, I now keep the Street Rod on a maintenance charger 24/7 as it mostly just goes to a few shows a year. When I measured the parasitic draw is was like 40 to 50 milliamps. It does have several micros like on the Dakota Digital Dash and the remote doors/window controller, the alarm, and the remotes on the sound system, that power the speaker amps and CD player.
Pic below is from my 2014 four volume service manual. Note a 50-milliamp parasitic draw will only keep the battery charged enough to start ~ 2 weeks. Also put a pic of my Street Rod wiring, I did from scratch.
Upper left are the sheets of the wiring diagrams I made. Bottom pic is behind the sound wall where I have power terminals for power when the car is shut off and when it's powered. Middle is under the dash where the Dakota dash meter controller, switches for ignition, lights etc, and switch for the two electric fans that are in front of the AC Condenser rad etc and Vintage Air system.
Nice custom hot rod. Very similar build approach I am doing on my '91 Z28. Dakota Digital dash, Vintage air HVAC, Flaming River column, Painless harness, etc...
Do you know the answer to my question about the C7 battery being essentially a vented FLA and therefore doesn't need a sealed and vented battery box?
I feel like FLA batteries are more conventionally reliable so if I can go that route and avoid the size/bulk of a battery box then that would really help me out. I need to fab up mounting brackets for the air ride air tank in the same general area so keeping things as small as possible is a priority.
Nice custom hot rod. Very similar build approach I am doing on my '91 Z28. Dakota Digital dash, Vintage air HVAC, Flaming River column, Painless harness, etc...
Do you know the answer to my question about the C7 battery being essentially a vented FLA and therefore doesn't need a sealed and vented battery box?
I feel like FLA batteries are more conventionally reliable so if I can go that route and avoid the size/bulk of a battery box then that would really help me out. I need to fab up mounting brackets for the air ride air tank in the same general area so keeping things as small as possible is a priority.
The OEM C7 I replaced is definstaly a FLA and only has a hose from the top to a hole on the rear floor. It's only covered by a carpet. That area would not be considered vented.
Pick of C7 OEM Battery. Can actually see hose on the left coming from a 90 degree plastic fitting. Yellow arrow is the plastic cover that covers the power board.
This is the rear fuse panel just to the left of the battery. The bottom of the rear floor carpet is on the let. There is a lose foam insert over the battery. It is showing and add-a-circuit used for the radar detector (red wire.)
After having some strange problems in my 2014, I took the car to "The Corvette Mechanic" in Middletown Ct. He noticed the AGM battery in the car and said that IS NOT the right battery for the car. A # 48 class lead acid battery is the only correct battery for that car. He said the car will not charge the AGM battery correctly and can mess with the values in the BCM. I had noticed some HIGH charging readings since putting the AGM in and will be looking to change the AGM out. Although the car seemed to run ok, when he was looking for certain values from the BCM he was not finding the correct values anymore.
That is completely false, and some of the most absolute garbage advice I've ever heard. An AGM does not mess with any values in the BCM. It is simply a more reliable battery, with a deep-cycle capability that can't be matched by a FLA model. My daily drivers have always been BMWs, which have a significantly more complex charging cycle than even new Corvettes, utilizing their infamous IBS system... But, in the end run, batteries are charged based on a set of voltage history tables and run values - Not whether it's AGM or FLA. Even in the BMW, a registered AGM battery simply gets a deeper cycle, but not by much. That mechanic should be ashamed giving such BS advice... Trying to sell you an FLA. There is no nned to register, or otherwise "tell" the car what battery is installed - The charging system is GM-run of the mill. Also, in every Chevy dealer I've been in, the AC Delco GOLD (AGM...) is on sale at the parts counter, with no "oooooohhh, don't install this in your magical Corvette" sign on it. SMH. Rant over, and out.
FYSA, I've used AGM batteries in every Corvette I've owned, really only driving them weekends, and have never had to use a charger.
^^^^ What a line of BS that mechanic handed out just to get a battery sale. Unfortunately some actually believe their own BS. The Optima AMG I installed in my C6 lasted fine for many years. Had to buy it because the OEM battery leaked with a crack in the case! Bought a Yellow Top because the car was Yellow!
The Craftsman AMG I installed in my 2014 C7 Z51 worked just fine. Had to buy it because the cheap OEM battery had a weak cell and was reading low in 2 years. Would not install another. Can't blame GM as they have to use low cost items where they can. There are better batteries either standard lead acid or AGM.
Just a quick update, of sorts... Advanced Auto Parts lists the Diehard AGM as a replacement for the C7. I just bought one today (June 1, 2024) for my '18 which still had the OEM from its summer '17 manufacture date.
What a line of BS that mechanic handed out just to get a battery sale. Unfortunately some actually believe their own BS. The Optima AMG I installed in my C6 lasted fine for many years. Had to buy it because the OEM battery leaked with a crack in the case! Bought a Yellow Top because the car was Yellow! 
