Right on! Have said this before too.

 

^^
FWIW, changed my 2014 OEM battery after 2 years because it had a low voltage from day 1. Got below 11.8 and was summer so changed to a Diehard AGM! Zero issues. Voltage measure 12.5 volts (measured 12 hrs after stopping to eliminate surface charge.) Don't buy the can't use AGM! BTW the 11.8 was 24 hours after it was on a GM equivalent CKET charger.

As noted in Post above I replaced my C6 battery that leaked with an Optima yellow Top AGM. Worked great and matched my yellow Vette!

Battery I bought. Note AGM word under long life!

 

People are just not understanding. Long life IF CHARGED PROPERLY! Look at the charging specs. They require a multistep charging program which our corvettes DO NOT have. So yes, long life......but only if charged in the manner prescribed by the manufacture. In the marine business, thousands of AGMs give out prematurely because Billy Bob installs a new AGM battery but has an old ferroresonant charger designed for leaded wet cell batteries. The boat box store never tells them about the charging needs of the AGM (and also gel cell batteries).

Now, if you have a huge stereo system or other large load that you like to use when the car is not running, deep cycle AGM batteries might be right for you. Not sure how you would upgrade the charging system to be compatible with AGM technology. Perhaps a voltage regulator mod of some kind. So you might sacrifice longevity for the ability to run those large loads with the engine off. Trade off.

Do as you will....

 

My AGM has been running strong for years. It appears to be recharging just fine.

 

Hear you BUT I have had only Yellow Top Optima's in my Street Rod for 22 years. Recently changed because it was ~9 years old and if at a Show would be a PIA to even get into the car IF I shut the door. Electric doors and windows and Optima is inside the car (at home have a way to get a door open from under a running board on a taped wire!

I have had only a $35 Schumacher maintenance charger on the battery essentially 24/7 unless going to a Show. Perhaps it was the usage but lots of power needed to turn over the 8.2 Liter BB, which after it has sat for a few months that 850 Holley double pumper is drained of fuel!

 

Just a quick note: The C7 does not know how to properly charge an AGM battery. This will not hurt the car, but the AGM battery will not be performing at its best.

 

^^^
Perhaps but either does my $35 Schumacher charger on my Yellow Top Optima in my street rod. The last was 9 years old when I replaced it only because of it's age! In fairness it stays plugged in 24/7 for all but a few days each year when it goes to car shows.

 

^^^
Please note I am not saying the AGM will fail or not provide acceptable service, only that it will not perform at its best.

A number of people here have installed AGM batteries and have been satisfied. Your use works for you as well.

I would not bother to put an AGM in a C7 as the car does not know what to do with it and will treat it as a standard flooded lead battery. Others are happy using an AGM.

 

Goodness.... You guys have really confused me... I wonder where one would go for correct answer to this question... A Corvette wit AGM batteries and charging them... That's the real question. My Schumacher good or no good for doing the job?

 

Just to add more confusion my C7 has a Duralast AGM battery that was in it when I bought it last year. However, the factory charger was missing. I bought a new one off of EBay and it is different from the C7 chargers I have seen. It has does not have the “Lead Acid Battery” verbiage on the side and it has a few additional state of charge lights. I’m guessing it is a C8 charger. Whatever it is it seems to work.

 

Exactly!
Personally, I don't understand using anything but the Delco OEM replacement. You typically get 5>6+ years out of them, easy to find and cost is reasonable.

 

^^^
This is my reason: I had to replace the OEM battery in my C6 because of a leak that lowered the level in a cell. Funny, GM had a duct built into the battery box and the service manual said "In case of a leak acid will go down past the electrical parts located under the battery!" (BTW had a similar case leak in an OEM battery in my S-10.)

For my 2014 Z51 had a low voltage from Day 1! Dealer without removing and checking it on a load bank said it was fine. In the summer after 2 years it was reading ~11.8 volts 24 hours after being "fully charged" on my equivalent to GM CTEK charger. The 24 hours is needed to check battery voltage to have the "surface charge" depleted that gives a false high reading. So before winter bought a quality Diehard AGM when it was on sale. Voltage was back to ~12.5 (after surface charge depleted) and car ran fine.

I have only used Optima Yellow Top AGM in my now 22 year old street rod that is mostly on a $35 Schumacher Charger (same Schumacher that has ~3 Dragsters and ~3 Funny Cars at NHRA National Events.) Nothing fancy and replaced the last a few years ago because it was 9 years old. Since I have electric doors operated with remote AND the battery is inside the car be a PIA to get in if it failed then!

When my C8 battery goes will buy a quality AGM! I seldom use my CTEK charger as it's my DD. Although retired and don't drive every day, when I do it's usually a ~50 mile round trip to town so the alternator keeps it charge. The Optima AGM it's NOT like a Gel Cell!
This is what their instructions say about using a battery charger:
"Under normal vehicle-starting applications, most regular automatic lead-acid battery chargers will properly charge an OPTIMA battery. "

Optima also make a battery just for the C7 (frankly I'll probably buy a lower cost AGM locally!) Yep in deep discharge applications AGM's can be charged to a slightly higher level as I recall. That is NOT Needed for normal use. Hope that clears up some confusion! Read what the battery manufacturer states BUT be careful they may be trying to sell you their charger. The GM (or equivalent CTEK like mine) is fine, IMO.
.

 

Unfortunately, you have bad luck in experiencing poor performance with Delco batteries. I literally purchased, warrantied, sold thousands of Delco batteries through my auto parts stores over 16 years and found their quality to excellent with a VERY Low defect ratio.
I've also had very good performance with Delco in my Corvettes over the years ranging from the old Tar-Top batteries in my old vettes to my C7 GS Delco being 4.5 years old when I sold it and never having a minute's trouble with it. I'm confident I would have gotten a couple years use out of it.

 

Is the battery compartment sealed and vented on our cars?

Don't you need this since the battery is in the "cabin" and not under the hood?

 

^^^
Did not see a hose to the 'outside' as was on the C7 battery. Perhaps I missed it but have had those covers off number of times. Assume sufficient openings as fluid leaks from the Lift Reservoir cap went onto the ground and it's in the same space. Can see the ground through some spots once you take off the three plastic pieces.

Unlike the C7, the C8 battery is not in the passenger compartment. However believe the vent is needed to prevent an accumulation of a pocket of hydro

SIDEBAR
Yep even an AGM battery needs to have a vent. The Yellow Top Optima I have in my street rod can be mounted sideways or even upside down has a vent. Unlike conventional lead acid batteries with liquid, it does not vent hydrogen UNLESS it's overcharged. Then the hydrogen pressure will build up and there is a high pressure valve or bursting disk that will release hydrogen. The AMG battery with which I replaced the OEM battery in my 2014 C7 had a place to insert the hose that went outside the battery area, WHICH WAS IN A CLOSED SEALED AREA. In fact is was so tight on my 2014 C7 that the "magic memory wire" activated memory vent (which was hyped by marketing) was not large enough and to get the hatch to latch I had to have a door open! It was finally replaced with the motorized pulldown I had on a C6 and is on the C8 hatch.

 

Gotta admit I am more confused now than before. Partially because I couldn't follow some of what you were talking about with reference to C6 and C8 vettes. I know nothing of these cars so I don't know what you are referring to.

As far as I seen aftermarket relocation kits for batteries all come with boxes and a vent tube for flooded lead acid batteries. When using something like an optima, you can just place anywhere with no vent. Since the C7 battery location is in the cabin and isn't in a sealed and vented box, what's the deal? This is really my main question. This sort of thing is of course not an oversight so I must be missing something.

 

YouTube: Project Farm
Did a good video on car batteries, titled "Which Car Battery is Best? Let's find out!"
I learned that many are made by the same companies.
I am leaning towards a Diehard AGM. Many will say stick with the ACdelco OEM, hard to disagree with.
I have to decide next year.
Good luck.

 

Sorry just saw I was in C7 not C8. But answer fits both. Optima Batteries CAN VENT!

I'll discuss with pics and info on AGM (Absorbed Glass Mat) batteries when used in the marine industry. Hope pics and that Marine info help your understanding!

First, I installed an AGM (that what an Optima is with a different shape.) in my C7. Both the OEM battery AND the AGM battery had a place for a hose that went from the top of the case to the outside bottom of the battery recess.


Quoting from a Marine Safety Info:
AGM batteries do vent! Quoting from a marine source- they should know: “Even though AGM batteries are normally sealed, they do have a venting system integrated into the case top. In the event of an overcharge condition, it is possible for excess pressure to build up inside the battery and then release after a 2 or 3 psi accumulation. If it occurs, hydrogen gas will vent and it is quite explosive.” A Vent is required by the Coast Guard even with AGM batteries like Optima.

That info come from the PDF re battery install on my C7 BUT has some basic battery info as well. Might be of interest to the Silent Majority who view threads (10 to 30+ times the number who post) if they are technically inclined: http://netwelding.com/Battery_Issues.pdf

So yep, even the Yellow Top I have had in my Street Rod for 20 years (3rd one) AND is inside the sedan passenger compartment (right rear over the tire in the sedan to provide some extra weight on the 16.5 ich section thickness (420 metric) tires for traction) it should be vented. I don't!
The Diehard comes with holes on both sides of the battery top. The OEM battery has a hose that exits out the bottom of the car. The 90-degree plastic hose fitting on the OEM battery fit the Diehard as did the OEM plug that fit the other hole on the Diehard. The 90-degree angle elbow fitting was placed on the hose that comes from the C7 battery well floor. It was tucked under the right-side carpet to clear the new battery during the install. After the battery install it was placed in the right-side vent hole by “feel” as there is little ro

This is a pic of the C8 battery where I disconnected the ground when changing brake pads. I have had the plastic cover off many times and have not seen a vent tube. BUT UNLIKE THE C7, it is NOT in the passenger compartment and there are openings to the ground like my 1988, 1993 and 2008 Vettes and most FE cars! GM states has to be done or you inadvertently open a door with the old pads out the electric power brakes (not vacuum assisted as in all prior Vettes) may activate with ~3000 psi pushing the pistons out and brake fluid all over- NO FUN. Again for techiees like myself.)


PS: Found This Pic. This should clear up the thought that Optima's don't ever Vent

 

^^^
Jerry good to see you back posting in C7

 

^^^
Thanks. Yep, I get emails from the Forum when someone posts on an old C7 thread where I posted! That is why I thought this was re a C8! Yep now up to 56 PDF's re How Too's and info with lots on C8 and C7. In fact, just checked and 17 of the 56 cover both the C7 and C8. Although there are some differences, installing side skirts and low dust brake pads still needed for both Z51s are the same! In fact, the C8 has the same very strong double-sided tape holding the front pads to the pistons as my early 2014 C7! I managed the same way I did for the 2014 with a stiff paint scraper and hammer BUT it's far safer to remove the caliper!

Pic from post 38.