Don't think there would be any issue running whatever the stock car runs for an optima, but figured it can't hurt to double check here.

Car will be used for shows mainly, air ride, no radio or AC, driven when it is nice out.

On that note, what is the stock size for a 91z28?

 

Dennis, you may want to read this before buying......

https://www.thirdgen.org/forums/afte...-batterys.html

 

AGM batteries are a form of Valve Regulated Lead Acid (VRLA) battery. A lot of people call them "sealed" but it's actually vented. Think more like "not serviceable" because the fluid can't be replenished when lost. AGM are electrolyte starved, meaning there isn't much fluid that can be lost before it becomes a problem. This makes the AGM battery life shorter than flooded lead acid battery in conditions where electrolytes are lost, such as hot weather and overcharging.

AGM batteries require a slightly lower charging voltage than flooded lead acid batteries. The alternators in our cars don't know that and overcharge the battery in hot temps. Combine that with the electrolyte-starved nature and you've got a battery that loses fluid quickly and doesn't last long in a hot engine bay. Flooded lead acid batteries are a far better choice for a starting battery in our cars because of the high operating temps in summer when most our cars are on the road.

AGM batteries are more tolerant to heavy discharge though. Normal starting batteries (flooded lead acid) hate to be discharged, even by 15%, and can't handle many discharge cycles. AGM batteries are much more tolerant to discharging and can handle on the order of 50x more moderate discharge cycles. And it will handle more deep discharge cycles too. So AGM can be an advantage if you're the kind of guy that parks their car a lot and lets the battery discharge. Basically it might help if you're a careless car owner.

The AGM won't give hardly any warning of failure because it will hold voltage pretty well until the day it's done. It's just the nature of the beast. That's why people feel like their battery failed without warning even though it was gradually losing capacity and wearing out. Flooded lead acid batteries have a different voltage curve with wearout and give more feedback & warning of impending doom.

Here's the bottom line: VRLA suppliers (not just Optima) are trying to get into the starting battery market. Their marketing spiel is AGM is an advanced lead acid battery that will provide improved starting over standard flooded lead acid batteries. But it's not true. The prices are 1.5 to 2 times more expensive than flooded lead acid batteries, and Optima is even more overpriced than standard VLRA batteries. And it does not give the cranking and life benefit for starting applications. Although it is a benefit in a cycling application where batteries are discharged.

 

Thank you for all the detailed info.

Here is the deal for my build, there is zero, and I mean zero in my car stock. Like no wiring, motor, trans, rear, suspension, brakes, wheels, anything. The unibody and the hatch are stock.

The engine bay is heavily modified for smooth sheet metal. I cut half the firewall out just to close up the heater core holes.

Saying this to just make a point that this is strickly a show car. If I ever drive far it would be on a power tour, and AAA would be ready and waiting. Car will be on run flats like my vette.

Battery NEEDS to be relocated to in the cabin. I could opt for a sealed and vented box and run a flooded battery but that would make the mounting of the 3 gallon air tank above it just about impossible. The other side need to hold the compressor. And my trunk well doesn't exist anymore since I altered the shape of the floor to accommodate a fuel cell so I could shave my gas tank door like 15 years ago.

The common "generic" size red top is 34/78. It is bigger than what is recommended for our cars. I don't care much about cost, but if there is another name brand that has a reputation for quality I will consider it.

I think the car may be driven like 3k or 4k miles a year

 

I have seen the Quality of most Products that I work with on a regular basis (Automotive Parts, and various types of Computer Electronics) drop over the last 10 to 15 years.

Everyone seems to be trying to cut cost to a point where quality suffers.
Products that I have never previously had issues with... are becoming problematic.

Also I seem to be experiencing a "Hit or Miss" type of success with many products.
I'll have good luck with one, and the next will be crap... find another good Unit, and then another bad one.

It feels as if it has been a long time since I found consistently good Products anywhere.

 

Automotive Batteries have been the same... Hit or Miss.

I believe that I have had relatively good/ consistent results with XS Power for Batteries.
...but who knows; you guys could have the exact opposite results!

It is difficult to have faith in many Products these days.

 

The lower battery temp inside the cab will help battery last quite a bit longer (whether AGM of FLA). Charging voltage will be much closer to ideal for the AGM and the battery will be happier. The overcharging of AGM battery gets worse as the battery temps increase underhood.

AGM has the fluid captured in the mat so it's safer from a standpoint of spilling fluid in a car accident. That would be a big factor in my head if I put a battery in the cab.

Regarding the starter motor, larger group size battery is fine as long as you're not getting too aggressive with the battery CCA rating. Avoid selecting a high CCA battery. All it does is increase the in-rush current when starter engages, which makes the starter snap to life quicker (more torque), and that can maybe slip the clutch or twist the output shaft. The starter does have a spec for max battery sizing and it is almost always dictated by the mechanical limitations of the starter to survive the torque at 0 rpm when starter first turns on. Those specs aren't available to the general public, so just stick with a battery CCA close to factory and you'll be fine.

Regarding the battery itself, people tend to think if some CCA is good then more is better. Really what you're getting is a less reliable battery with thinner plates that are more prone to issues. Go for the lower CCA battery within a battery group size. You'll get thicker plates and battery will last longer. Larger battery capacity is a good thing that will extend useful life. Larger CCA is worthless if the starter doesn't want it.

 

Noted all the info about CCA. From what I see on Optima's website, there are not multiple batteries that are the same size but have different CCA.

Really the descition is to get the smaller unit that was the direct replacement for the car stock, or the more generic unit that is slightly larger.

The car will have a brand new LS3/T56. So basically a 5th gen Camaro SS powertrain. Stock started and all. Since this is very vanilla, I am going to guess the conventional Optima red top will be fine. I will call Optima to confirm this on Monday.

There are some very trick battery hold downs for optimas that lend themselves well for custom clean installs in the spare tire well area of the car.

Little clamps that grab the foot, leaving the entire top of the battery free of clamps. This means I get more clearance for the air tank brackets.

 

Dennis, I gotta ask, , , did you read the thread I linked in my first post? I have enclosed a post from a fellow TGO member whose opinion is very well respected, he owns a custom car shop and builds cars like your building and his battery of choice is the Odyssey VS the Optima. Why would you want a battery of suspect quality when a better alternative exists?

Anyway, your dollars your choice, I just wanted to make sure you were making an informed decision VS being drawn in by the once great "Optima" name. I'm out........

 

Maybe baseline things by looking at what is used in a 2010 Camaro SS. I think battery is even in the trunk.

I encourage you to call and talk to battery sellers, but I'll warn you that battery manufacturers will sell you anything whether it works or not. It's one of the world's great mysteries how they can be so ignorant about the starting & charging applications where their products are used. You've got to talk to the starter & alternator people for the real story. There is no phone help line for that but GM engineers left you clues in the cars that use LS3 engines.

 

My daily driver is a 2015 Corvette C7. It has the battery in the back under the carpet. In the passenger compartment.
It is not in a sealed and vented box.
Turns out the battery itself is sealed and vented!
It is like the best of both worlds. FLA, vented and cheaper!!!!

Gonna do what you said QwkTrip and compare the OEM battery specs of the C7 and the fifth gen Camaro to see if they are close.
If I can just use a C7 battery and vent that, then that is what I am going to do. Would mean replacements will be easy to find too!

 

I fell for the Optima spiel and used to only run red tops, but they died in less than a year. The only Optima I had long term success with was a blue top to power the trolling motor on my jon boat. I ended up dumping the Optimas for a Die Hard from Advance a couple years ago. I haven't had a problem since.

 

I have a AGM battery (in another car) made by DEKKA (they don't offer the AGM for thirdgens). I installed it in April of 2013, and as of January 2022, it is still going strong (nearly 9 years). This car spends more time sitting than being driven (only a few times during the summer season), so I don't know how that affects the longevity. It's not like the car has been started hundreds of thousands of times. But I'm pretty happy with it. It was $170 in 2013 (I'm sure it costs more now) and I think I've gotten my money's worth. I like the fact that it doesn't leak acid and rot the battery tray. I have a regular FLA DEKKA battery in my thirdgen. 'Had it less than 2 years so will have to wait & see...

 

Nice. Thanks for the experience.
I have had good luck with a red top in the past.

Online stories would make you think none of them work.

I have also never had a FLA battery leak, ever, not even a drop. Lucky I guess. This is a show car so it will most likely live on a trickle charger it's entire life.

I am setting up the battery situation exactly how my C7 is. A vented FLA battery. No need for a sealed box. Can always swap to an AGM someday if there are any issues. I doubt there will be.

Follow my build thread if you wanna see how I turn the spare tire well into a factory lookikg battery compartment.