I have a question. The standard battery in the Stingray is not AGM, right? So, the charging controller knows how to charge that. How does it know that you switched to AGM and that it is a new battery? On my BMWs, you had to code the type of battery if you switched types and you also had to tell the car (programming) that you put in a new one, all of that to ensure the car does not cook the replacement battery. None of that is needed with the C8?

 

Don't know if the battery monitor automatically detects if an AGM battery is installed, the service manual isn't clear. An AGM battery does require a slightly different charging profile for optimum charging but in real life use it doesn't seem to matter. AGM batteries work fine in the C7 and I expect the C8 also.

 

So that it does not overcharge it?

 

AGM batteries have a slightly higher charging voltage so, if anything, it would be slightly undercharged.

 

Optima Red Top here.

 

Agree.

I would install an AGM battery with no concern if that is what I wanted. In my case, I think I would replace the battery every 4-5 years (max) regardless though, so I see no particular advantage to installing an AGM over an FLA.

I agree - the Service Manual description of the charging system operation is not clear on whether it can detect and adjust to a battery with a different specification. There are some things we can observe about that. There is a scan tool parameter (and many are generic, not unique to a specific make/model vehicle) to indicate the battery type, The 2020 C8 service manual says the correct setting for that is default (not FLA, not AGM etc). And, the instructions for battery replacement do not include anything about it being necessary to tell the car what type of battery is being installed. It does, however, call for a very, very simple "battery sensor module learn" procedure - let the car sit for at least 4 hours, after which it will automatically assess the battery state of charge using the "resting voltage". What is interesting though, is that in the list of reasons for the battery sensor relearn procedure, it includes this statement:

".....the Battery Sensor Module will require the calibration procedure to be performed. Examples are:
The battery was replaced by a battery with the same part number
The battery was replaced by a battery with a different part number or different specifications
The battery was charged while outside the vehicle
The battery was discharged while outside the vehicle
The battery was improperly charged".

Does "different specifications" include AGM? Who knows?

We know that many many folks use AGM in thier C8 with no problem - I used the Optima Yellow top in my C5 with no problems ever.

And as noted, the Charging System seeks a SOC of around 80% in the Economy Charge Mode - based on the description in the Service Manual - so if the car targets the FLA voltage for that - the AGM SOC would be slightly less than 80% - no one has ever reported a problem. So if it does not detect and adjust for battery type, the AGM will be slightly below the target state or charge (like you said).

Two big differences (not the only ones of course) between and AGM and FLA are the internal voltage and the internal resistance. While it does not say so in the service manual, it is possible to estimate both of those by measuring charging voltage and charging current and two (or more) different charging voltages (which would need to be done with the engine running). I do not know if the car does that. The manual says it looks at resting and charging voltages and current in and out of the battery, and uses that to keep a running estimate of the battery SOC, but it does not explicitly say it adjusts for battery type.

 

This is what I do

 

Yah, this is where I am at. I stick with a conventional battery from a source I can easily get a warranty exchange if needed. Instead of the high cost AGM batteries I just look at the battery as a 3 year replacement item based on learnings from other keyless start vehicles. Not sure if there's quite enough info on the C8 to know if we can stretch that a bit, but many GM keyless vehicles just seem to eat batteries, and I'd rather replace a regular cost one a year early than deal with the hassle of it dying.

 

Tale of Two AGM Batteries:

I got an ACDelco 48 AGM battery from Amazon that arrived with less than 10 volts with no country of origin noted and no visible date code – so it was returned. I then bought a Deka 48 AGM from Rock Auto that cost about $20 more but arrived with 12.7 volts along with a 4/25 date code and made in USA. 6 hours after a trickle charge, it was at 13.1 volts and ready to go into my 2021 Z51.

Bill

 

Always check your specific AGM battery for any recommendations; I currently have 5 generic AGM batteries in vehicles that never came with them (including 1 motorcycle); Most of the time you'll never have an issue, with one or two exceptions; AGM batteries have a fairly low internal resistance, so it's possible to exceed the recommended charging current if the battery is deeply discharged.

Under normal starting and driving, the AGM battery output voltage is close enough to the alternator voltage that the charge current into the low-resistance AGM battery isn't high enough to cause the battery to heat up or otherwise cause issues. The alternator may not charge the AGM battery to its max charge voltage, but that's normally OK as the alternator output voltage is high enough to avoid sulfation.

If you ever deep-discharge the AGM battery to the point where the Vette won't start, use it in an RV and deep cycle it, have it go dead in your garage, or otherwise experience a dead battery, avoid the urge to jump start it and drive it to charge it back up (although an occasional emergency jump-start probably wont hurt it). A standard lead-acid charger or alternator may drive too much current into a deeply discharged AGM battery, creating heat and there could be sulfation issues as well. In this case, an AGM charger is recommended. AGM chargers have a specific current-limited charge profile which can desulfate and and bring it back to full charge without overheating it. I like this CTEK since it does smaller AGM powersports batteries as well, and I can use it as a battery tender on the vehicles I'm not driving. There's also an anti-sulfation cycle when the charger starts, which can help recondition a battery in case of a sulfation event.

 

I used an Optima Red Top in my C6 for 14 of the 16 years I owned it and never had any charging problems. I went to the Optima because I had the original OEM and the warranty replacement OEM batteries both split and spew acid into the engine compartment.

 

That long ago Optima's were good but no longer.

 

Antigravity battery. They only weigh 12 pounds, they last longer between charges for a storage, they have a dead battery push button to start your car, but they are a bit expensive.

 

For your 2022 car, the best replacement is an AGM (Absorbent Glass Mat) battery from a reputable brand that matches the correct size and specs for your vehicle. Common top‑rated options are Optima, Interstate, DieHard Platinum, or ACDelco AGM.

 

I would like to also add that in the past 30 years I had been driving german cars which had AGM batteries. With prudent top-offs in the winter with my charger, all the AGM batteries lasted about 10 years.

 

Yep toured the Johnson Controls battery plant in town "when it was owned by them." They sold their Lead Acid battery operations to, see quote:
Johnson Controls completed the sale of its Power Solutions automotive battery business to Brookfield Business Partners L.P. and institutional investors (including Caisse de dépôt et placement du Québec) on May 1, 2019, for $13.2 billion. The business was subsequently renamed Clarios.

Clarois was also in the battery business and has plants all over.

BTW, the plant manager conducted the tour and when we watched folks at the end of the assembly line putting different labels on the same built battery asked what the differences where as some offered 3 and others 4 year warranty. He said we give one warranty to the selling dealer. You're paying "Insurance" if they give more! They did make several types and supplied on a JIT basis. Sears, AutoZone, etc sells a battery their trucks were delivering a new replacement a few times a week and picking-up old ones.

I bought a Diehard AGM for my 2014 C7 because it was on sale. Found the same one at AutoZone with another brand name!

BYW, don't think about the E-Ray 12 volt Li-Ion battery. The car charging system is different and it's very expensive, no brand name only from GM. Get one designed as a Lead-Acid battery replacement. Frankly IMO a quality AGM is a better choice.

 

At 4&1/2 years I replaced the original, factory installed, battery with another, dealership supplied and installed battery. In another 4&1/2 years I will do it again.

Nothing exotic or special. Just a replacement battery to function as the original .

On past Corvettes I have used Optima red top with success as well as other, aftermarket AGM batteries. No problems with any of them.

 

Right now the best deal I have found is the Interstate AGM at Costco for $179, the price of most lead acid from most others. The next best is the WalMart AGM at $189. The advantage of the WM battery is if warranty needed, there are WMs everywhere. Over the years I have had a number of warranty replacements from all brands and if on the road convenience is a plus!

 

Since "identical" battery performance can vary all over the ballpark... no matter the price, it is something of a crapshoot. Get a good quality, known brand, but even that's no guarantee (don't ask how I know); and, drive on!

 

If my Corvette is not going to be used for more than 3 days i connect my Deltran Battery Tender. I have been doing this starting back with My 1989 C4 and have Batteries Last 10 years. My 2015 C7 was 8 years old when i Traded in for my 2023 C8 still had its Original Battery !!